Is it feasible to remove the skimmer? Could it solve the decades-long problem of nutrient accumulation?

[jda]

The last phase of the nitrgen cycle of turning no3 into N gas is limited only by surface area, IME. In a tank with real functioning live rock (not dead/dry that is filled with organics and even terrestrial phosphate which does not allow anoxic bacteria to colonize), I have not met a bio load yet that could not get kept down naturally. Bare Bottom tanks already have limited surface area. I once had a 300ish G with about 30 fish in it - mostly larger tangs that ate coral (yes, tangs often eat coral as they get large), triggers, gunea fowl puffer and two basketball sized lions. I fed this tank so that they all fish grew and were not aggressive - kilos of raw food a week and a 5lb pail of pellets every month. This tank had no3 under 1 because of the few inches of sand and live rock. Phosphate was another thing and it climbed and climbed and the rock and sand got SO saturated - eventually all of the macro died and even the coralline... I was probably above 2.0, but just guessing. I bought a 55 gallon drum of the aluminum oxide that was used in bulk to dry air (or something like that?) and changed it out every day or two for about 5-6 months and about 30 gallons of media later was down under .1 and the coralline started to thrive again. I still use that rock today that was once SO loaded with P and now has a very low concentration - some of it was from the GBR back when you could get rock from there and some from Marshall Islands which was the best rock ever imported.

 

[HuduVudu]

It just works for me and in no way would I say that anybody has to have one, but I would say that they need to deal with things in some form and just not do anything. ...kinda like the DSR folks - they work hard not to change water and are just not lazy and do nothing (how is that for another false equivalency).

OMG this hobby in a nutshell.

So often novices want to defend to the death the "team" that they belong too. The truth is more nuanced than that and there are as they say many ways to get a cat skinned.

I believe that by understanding the underlying idea then all options that you can dream up will be available to you. Everyone's circumstances are different, but everyone wants to succeed. For this they come up with different ways to solve the problems.

 

[HuduVudu]

Ok, so I had to know ... what is my free Phosphate.

Survey says ....

.1ppm

 

[Nano sapiens]

The last phase of the nitrgen cycle of turning no3 into N gas is limited only by surface area, IME. In a tank with real functioning live rock (not dead/dry that is filled with organics and even terrestrial phosphate which does not allow anoxic bacteria to colonize), I have not met a bio load yet that could not get kept down naturally. Bare Bottom tanks already have limited surface area. I once had a 300ish G with about 30 fish in it - mostly larger tangs that ate coral (yes, tangs often eat coral as they get large), triggers, gunea fowl puffer and two basketball sized lions. I fed this tank so that they all fish grew and were not aggressive - kilos of raw food a week and a 5lb pail of pellets every month. This tank had no3 under 1 because of the few inches of sand and live rock. Phosphate was another thing and it climbed and climbed and the rock and sand got SO saturated - eventually all of the macro died and even the coralline... I was probably above 2.0, but just guessing. I bought a 55 gallon drum of the aluminum oxide that was used in bulk to dry air (or something like that?) and changed it out every day or two for about 5-6 months and about 30 gallons of media later was down under .1 and the coralline started to thrive again. I still use that rock today that was once SO loaded with P and now has a very low concentration - some of it was from the GBR back when you could get rock from there and some from Marshall Islands which was the best rock ever imported.

To showcase how variable reefing can be, 13 year 12 g and I have only seen a very low PO4 reading a handful of times (almost always 'undetectable'). Mostly 20+ year old LR/LS. On the other hand, in the last few years NO3 has risen from a consistent 1-2 ppm to 10-15 ppm (due to various factors).

Interesting hobby

 

[happyhourhero]

No skimmer

 

[Belgian Anthias]

Skimmers are great at mechanical export of nutrients same as filter socks or just changing filter floss like I did when I started in the early 70s using a corner box filter. Graduated quickly to undergravel filters then canisters. Success with those two revolved around contact time to allow nitrification to remove all dissolved oxygen leaving only bound oxygen such as nitrates and sulfates for heterotrophic bacteria to utilize why consuming carbon source items such as detritus. It worked although at the time i didn't grasp one needed nitrification to exhaust the DO.

Fast forward the demise of the UF because it's cheap and many believed it created dead zones because it trapped detritus due to not grasping decomposition and the evolution of more profitable sophisticated equipment evolved with the realization that carbon dosing could eliminate nitrates and phosphates. Ironically that is performed by adding back carbon which was removed by skimming and filter socks.

Build a large enough filter to contain enough filter media and slow enough flow to ensure extended contact and that filter will remove ammonia, nitrites, nitrates and phosphates as well as balance alkalinity since denitrification adds back base where's nitrification adds acids. BTW, that brown mulm we hate so dearly contains calcium, magnesium and other elements essential to life that was introduce through feeding. Leave it there long enough and through mineralization it will be released back into the environment. Nature wastes nothing nor does it create. Same as energy. All gets transferred.

I'm conducting a proof of concept using a 20g without water changes, no skimmer, no socks, no sump, no carbon dosing just water top off plus overfeeding 3-5 times per day. PH remains around 7.6 but that's because I'm struggling with aeration. Something that is of great benefit with skimmers but can be accomplished through other means. Ammonia and nitrites remain undetectable, nitrates remain below 20 ppm to 10 ppm. I know some consider that high but I don't. PO4 is under 0.25 ppm, test kit doesn't read lower but I'll be upgrading that soon. I'm good with below 1 ppm. My concern is more about the Redfiled ratio now that 'm starting to grasp that. Although if I was growing sticks then perhaps that might matter. I'll have to see and yet likely not a problem.

If I wanted to do away with the skimmer then I'd remove the socks as well. Add pumice (Seachem Matrix) to both compartments including the syphon box and just let nature decompose detritus as it has for billions of years. It's how UF worked until we added power heads and constantly disturbed the bed trying to vacuum the detritus because clinical seemed logical. Yet nature doesn't work that way.

Skimmers are not very effective TOC removers, comparable to the removal of DOC. Also the removal of TOC seems to be very selective.
Most in line skimmers are poor aerators,
Struggling with aeration? A simple airstone will provide enough water circulation and surface breaking for efficient gas exhange.

Carbon dosing with carbohydrates does not remove nitrate, fast growing heterotrophic bacteria prefer to use ammonia as a nitrogen source. it will limit nitrate production and may remove the nitrification capacity. As it is growth based it can not remove all released inorganic nitrogen if a skimmer has removed part of the other elements needed.
Adding carbohydrates will change the nutrient availability for slower growing organisms drasticcaly and mess up the existing balance completely. Not advisable for the purpose it is often used, for removing safely stored nitrogen.

I do prefer to keep the nutrient reserve as low as possible but measurable, I try to prevent the nutrient reserve is responsible for phosphate to become the growth limiting factor. I prefer nitrogen to be the growth limiting factor.

Socks and filter-screens do not make a difference between polar and apolar compounds, between hydrophilic and hydrophobic. They do not remove DOC.
Also socks or any other mechanical filter will prevent that biofilters, algaefilters, wil be able to remove all by fish and other organisms directly in the environment released anorganic nutrients. To be able to do this when making use of filter socks or any other mechanical filter for removal of particulate bio-waste, algae filters or and biofloc may be fed with for nitrogen or and carbon modified feed media , depending of the type of growth targetted to remove the nitrogen .

The nutrient balance? The balance between producers, consumers and reducers?

If 20ppm nitrate is present one can not remove this if only 0.25 ppm phosphate is available, it will be enough for assimilating +- 2.5 ppm nitrate, this if all other essential nutrients are sufficiently available. Also this can be adjusted using a for the target nutrient modified feed-medium.

Nitrification, removing ammonia not used up by heterotrophic growth, may lower alkalinity, depending on the substrate on which nitrification takes place. This means, using biofilters, one is able to manage the effect of nitrification on alkalinty as desired.
The consumption of produced nitrate will increase alkalinity. This means if all produced nitrate is consumed by growth, the system stays buffered.
In normal nitrifying remineralization filters +- 15 % of produced nitrate may be exported due to anaerobic remineralisation ( denitrification) and by autotrophic removal of in the biofilm produced HS and sulfur ( BADES)

Does the fact using a skimmer is making it impossible to use up all released inorganic nitrogen, also makes it responsible for not being able to stabilize alkalinity by growth. ?

 

[Belgian Anthias]

I better understood this than the post about skimming.

BTW you are sound like Paul B.

So your contention is that sensitive corals use NH3 and not NO3, and it is better to provide this through serious feeding with good export?

Also corals can use NO3 but must convert it back to NH3 which is too expensive for sensitive for corals?

All organisms able to use inorganic nitrogen prefer ammonia as a nitrogen source as they need to produce a lot more energy for to be able to use nitrate as a nitrogen source. In the case they have to transform the nitrate to ammonia internally.
Corals are heterotrophs, retrieving nitrogen from organics.

 

[HuduVudu]

An interesting video that I remember discussing Phosphate because this seems to be an area of discussion.

 

[Belgian Anthias]

Since P gets into this too. There are many kinds with organic/inorganic/phosphate/phosphorous. Different stuff prefers different kinds. Your test kit only tests for one. You get a variety from the fish waste too. All that we know with test kits and supplements is for that one kind. Some say this is no big deal, some say that it is... who knows. I don't know much beyond that heavy import and heavy export works and my stuff grows like crazy with very low residual levels - there are numbers and photos in my re-build thread but I do need to get some updated photos.

As for the metals, there is no doubt that some traces get skimmed out. Necessary, or not, who knows with a lot of these. I am mostly talking about the toxic ones that nobody has an argument that are good. It does seem to be that too little of something like zinc is better than too much, so skimming would help with something like this, but so can other things and you don't need a skimmer for this.

I guess in the end, I use skimmers because I am cheap and lazy, just like water changes. A 50 gallon bag of IO costs me less than $10 and a less than 2 minutes of turning knobs and stuff and this saves me who knows how much in supplement cost (red sea or KZ is not cheap) and all of that time dosing. Skimmer, I guess, is the same way. Sure, I can do the same thing with other stuff, but I bought some of these skimmers more than a decade ago, they just work and all that I have to do is empty a cup every so often rather than change GFO media every day (would literally have to), remember to put GAC on to remove chelated toxins, etc. It just works for me and in no way would I say that anybody has to have one, but I would say that they need to deal with things in some form and just not do anything. ...kinda like the DSR folks - they work hard not to change water and are just not lazy and do nothing (how is that for another false equivalency).

Which are the toxic ones? Does a skimmer makes the difference?

If all released nitrogen can be used up also most phosphorus is used up. All what is needed is sufficient growth, prevented by using a skimmer.
In a reef aquarium Phosphorus is best not the growth limiting factor.
Nature has arranged this by continuously exporting some nitrogen. from the tank.

Be carfull when using GFO.

 

[Dan_P]

The role of a skimmer?

My father had a saltwater aquarium in the early 1970s, based on Frank De Graaf's book, manual for the tropical marine aquarium, published in 1969. The aquarium was equipped with a counter-current skimmer. Since then, a skimmer was always in use. What has been established is that accumulation of inorganic nutrients such as nitrate and phosphate has been a perennial theme since then. However, that does not make sense, as the nitrogen is naturally constantly exported through denitrification and in fact a deficiency should occur if natural marine food is used. It is possible that food provided contains far too many of these substances, so that not everything can be used up and left behind due to new growth. Such nutrients then have a very low C/N ratio and usually contain an unnaturally very high protein content.

One can NOT keep fish in a small closed environment without exporting what of the added food was not used by the fish. A skimmer only removes +- 35% at best. of biological waste, whether dissolved or not. A mechanical filter only removes undissolved organic waste. Nothing is removed from what is not in the water column. If all goes well, there is sufficient remineralization capacity and growth, the total bio-load will increase constantly, if not regularly harvested. By using a skimmer, some of the inorganic nutrients and trace elements already present cannot be used up through growth.
Fish are fed and +- 85% of the nitrogen content of the food ends up in the closed environment. Mostly as inorganic nitrogen compounds which are not removed by a skimmer. To remove this nitrogen, of which +/- 15% will escape through natural denitrification, most of the TOC and DOC produced by the fish must be able to be remineralized and reused through growth. This is NOT possible when using a skimmer. Therefore, a skimmer creates an imbalance and accumulation of inorganic nutrients.

Disruption of the nutrient balance by the skimmer makes it impossible for everything to be used up by growth and harvested as needed. Certain nutrients and trace elements can slowly build up in this way to a toxic level.
Removing the skimmer does not restore the existing nutrient imbalance it has created during the period it was in use. This can be corrected by active algae management, AAM

Starting a new system without skimmer?

A coral holobiont will produce CO2 and other inorganic nutrients used by the symbiodinium, a result of remineralization of the DOC available there. Corals are able to supply their holobiont with organic matter and regulate the supply of DOC by excreting mucus. In this way the production of sugars by the symbiodinium is also regulated, a supply of sugars that the coral eagerly uses. A high level of dissolved organic substances in the surrounding water makes it impossible for the coral to regulate the supply as required. Therefore, dissolved organic matter (DOC) levels should be kept as low as possible where corals grow. In the ocean, the level of nutrients present in the surrounding water may be very low, but the supply is inexhaustible.

In an aquarium there is a constant production of DOC.
In the absence of a skimmer, more DOC is produced and more DOC must be remineralized, and more new growth must be harvested to keep the bio-load in check. But the nutritional balance can be restored, nutrient accumulation can be prevented.

Is it feasible to remove the skimmer? Could it solve the decades-long problem of nutrient accumulation?

i like your post. There are many, many ideas to address, but I will just provide a short response.

You can remove a skimmer. It will not solve any problems though because most problems arise from what the aquarist does, not what a piece of equipment does.

 

[jda]

I don't think that anybody can make any reasonable argument that nitrate or phosphate/phosphorous in all of their forms are limiting anything in our aquariums. Carbon is, and even then, it might have a purpose to slow down skeletal growth so that organic tissue can keep up. In nearly all cases, N and P build up well beyond what can even be removed with a skimmer and other natural means, like a fuge. Even in an environment where nitrate is processed by anoxic bacteria, they always leave enough to keep the equilibrium moving forward. I have never been able to get to zero with natural methods - ever.

I have had discussions with Ross on here about his tank and videos. You might be able to search for them. He will flat out tell you that his P numbers come with a limited set of corals that he can keep and he has lost many others along the way as the P levels rose. This often gets overlooked, but again, totally doable if you understand what you are getting into and manage your expectations about what you can grow with P that high... it is not what you are growing with lower levels. He appears to have become somewhat miffed that people have used his tank as a how-to book or reassurance that high P does not matter and most have not read the fine print. The last that we chatted, he was working on lowering his P levels.

 

[HuduVudu]

@jda I looked for the discussions, but I don't have the specifics to limit the number of results. If you are ammenable I would be interested in reading them.

You talk a lot about the ability to grow certian corals at lower P, what are those corals (a brief list off the cuff is fine) and what do you think that they share that makes them this way?

I don't want to dump work on you so if you don't want to respond that is kewl. I have a lot of fodder to consider with what has been said already.

 

[jda]

Happy to chat, but you are right...probably take this elsewhere. His name on here is thales if it helps with the search.

 

[HuduVudu]

Found one.

QUESTION OF THE DAY - Angry Phosphate Man: Mitigating High Phosphates In Your Reef Aquarium

Today let's talk about.......Mitigating High Phosphates In Your Reef Aquarium...dum dum dum! Angry Phosphate Man The first thing we need to get out of the way is that fact that phosphates is not something that can be avoided. It can't be avoided but it can certainly be minimized. Why is...

www.reef2reef.com

 

[jda]

If 20ppm nitrate is present one can not remove this if only 0.25 ppm phosphate is available, it will be enough for assimilating +- 2.5 ppm nitrate, this if all other essential nutrients are sufficiently available. Also this can be adjusted using a for the target nutrient modified feed-medium.

Your point that you need both N and P to grow organic matter is well taken. However, the numbers are not really accurate since if a tank had .25 of water level phosphate, there is a massive amount bound in the aragonite that will get released when you start to lower that water level. In the end, probably more phosphate left over even if you took the N down near zero.

Aragonite as a P reservoir should not be overlooked as an intended consequence of not exporting enough. It can take a massive amount of media down the road to get it out later.

 

[ceaver]

I do not need pics!

What I do need from skimmerless reefers, from those who never had a skimmer or have removed it since a long period, minimum a year, is information about the accumulation of nutrients in their systems and what they are feeding, protein content, from marine origin or not, etc..

Information about how skimmerless reefers manage their tank, how the bio-load and carrying capacity is managed, filtration?

All info is welcome.

So admittedly, recent aspects of this post have gone beyond my understanding, though I wish that weren't that case and I'm trying to keep up. Not enough background in bio/chem.

But more to the original thread title and post quoted here, I run an AIO 40 gal IM Nuvo. No skimmer for about 5 years, tank and rocks are about 20 years old. I ditched the sand and went bare bottom about 2 years ago. I use felt pads in the media baskets, changed twice a week. No refugium. I only rarely used carbon, until just recently (like 2 weeks ago) got a little reactor and some pellet carbon. Good flow and surface agitation.

I feed my fish a lot, quality pellets; frozen PE mysis, angel mix, LRS reef frenzy, and spirulina brine, all soaked in selcon. Have been dosing Reef Energy AB+ for quite a while.

I actually never measured nitrate and phosphate until recently, after the sand came out. Everything was at 0. My seasons greetings monti was very pale green at the time. Started dosing nitrate and phosphate and it bounced back. LPS started looking better, too. Since then I've ramped up sps stock a lot, still have to dose or else nitrate and phosphate bottom out. Tried stopping phos once and it dropped too quickly, everything paled, and a tricolor valida STN'd, which I read they were sensitive to.

So I'd say all the nutrition and nutrients going in are being processed naturally with no skimmer, no fuge, no GFO, and generally no carbon until a week ago. Perhaps this info is relevant to your initial question in the thread (or others raised along the way)?

Cheers!

 

[GARRIGA]

Skimmers are not very effective TOC removers, comparable to the removal of DOC. Also the removal of TOC seems to be very selective.
Most in line skimmers are poor aerators,
Struggling with aeration? A simple airstone will provide enough water circulation and surface breaking for efficient gas exhange.

Carbon dosing with carbohydrates does not remove nitrate, fast growing heterotrophic bacteria prefer to use ammonia as a nitrogen source. it will limit nitrate production and may remove the nitrification capacity. As it is growth based it can not remove all released inorganic nitrogen if a skimmer has removed part of the other elements needed.
Adding carbohydrates will change the nutrient availability for slower growing organisms drasticcaly and mess up the existing balance completely. Not advisable for the purpose it is often used, for removing safely stored nitrogen.

I do prefer to keep the nutrient reserve as low as possible but measurable, I try to prevent the nutrient reserve is responsible for phosphate to become the growth limiting factor. I prefer nitrogen to be the growth limiting factor.

Socks and filter-screens do not make a difference between polar and apolar compounds, between hydrophilic and hydrophobic. They do not remove DOC.
Also socks or any other mechanical filter will prevent that biofilters, algaefilters, wil be able to remove all by fish and other organisms directly in the environment released anorganic nutrients. To be able to do this when making use of filter socks or any other mechanical filter for removal of particulate bio-waste, algae filters or and biofloc may be fed with for nitrogen or and carbon modified feed media , depending of the type of growth targetted to remove the nitrogen .

The nutrient balance? The balance between producers, consumers and reducers?

If 20ppm nitrate is present one can not remove this if only 0.25 ppm phosphate is available, it will be enough for assimilating +- 2.5 ppm nitrate, this if all other essential nutrients are sufficiently available. Also this can be adjusted using a for the target nutrient modified feed-medium.

Nitrification, removing ammonia not used up by heterotrophic growth, may lower alkalinity, depending on the substrate on which nitrification takes place. This means, using biofilters, one is able to manage the effect of nitrification on alkalinty as desired.
The consumption of produced nitrate will increase alkalinity. This means if all produced nitrate is consumed by growth, the system stays buffered.
In normal nitrifying remineralization filters +- 15 % of produced nitrate may be exported due to anaerobic remineralisation ( denitrification) and by autotrophic removal of in the biofilm produced HS and sulfur ( BADES)

Does the fact using a skimmer is making it impossible to use up all released inorganic nitrogen, also makes it responsible for not being able to stabilize alkalinity by growth. ?

I have a much simpler understanding of decomposition. Provide an environment to allow nitrification to exhaust DO to the point heterotrophic bacteria are forced to use bound oxygen in an anoxic environment. Nitrates being favored before sulphate. How phosphates are utilized still beyond my grasp although I know life forms do require it. Not sure if the oxygen bound on phosphates also utilized.

My understanding of the Redfield ratio is that of 16:1 nitrogen to phosphorous or in our world being 10:1 nitrates to phosphates. Have also read 20:1 acceptable. Seems we are still trying to figure this out.

Putting the science aside. My learning is mostly based on experience. I must confirm. Seems often what is quoted isn’t always how it works.

Had 160 to 200 ppm. Tried lowering with NoPox since I just finished the Fishless cycle and had no detritus present. Added MB7 to seed the heterotrophic. Had zero success dropping it. Then discovered the Redfield Ratio. Oddly something I’d never heard of before yet been at this and trying to learn how to keep life in a box for almost fifty years. Bough the API test kit because only one that could read high enough once I added NeoPhos to bring my levels inline. To my surprise the nitrates read below 10 ppm and phosphates below 0.25 ppm. These kits aren’t extremely accurate and I Wes just seeking confirmation it worked.

Raised nitrates again to 160 ppm by using food coloring. Once again increased phosphates. Now I added two Sailfin mollies and fed them heavily using no additional NoPox but did keep adding MB7. Once again dropped nitrates and phosphates to the prior low settings. Been maintaining them until I got the ugly brown phase and concluded I must have silicates. Decided to use Phosguard just to see if it worked. Problem as existed us that it has bottomed out my phosphates to almost undetectable but now my nitrates are slowly rising which adds more confirmation to the Redfield ratio.

It’s proof of concept Tank and purpose is to stress test it and see what happens. Helps design my eventual display tank void of sump, skimmer or socks.

I’m aware of how to increase aeration but filter used and proximity to my computer and monitor are a concern because of splashing. Since this won’t be used to grow coral I’m not concerned with my PH although I’m going to try raising it with Alkin8.3. I’m also going to test using a lid bs being open to keep the splashing down yet increase surface tension to allow better gas exchange. Air stone not an option.

One other addition I made was using Reborn as my initial substrate where most of the nitrification will take place. Hope is that acidification from that process might melt some of the old coral skeleton and buffer the system similar to a calcium reactor although no way to confirm that. Just seems logical.

Do know this. My alkalinity was at 14 dkh requiring Seachem Acid Buffer to convert alkalinity to CO2 to reduce back down to 10. Considering nitrification uses large amounts of alkalinity that is promising.

Goal is to have a more natural process to maintain life so I can enjoy my living art without being a slave to my passion. Some love that aspect. I’m not even a fan of testing and know from experience that once something is balanced there’s less need for tinkering. Although display will have one of those automatic testers. I love technology. As well as keeping it simple and maintenance free or reduced greatly.

 

[malacoda]

@jda Do you find that skimming (you mentioned you employ 3 skimmers) is enough to keep your residual phosphate levels in check? Or do you also employ other means of reigning in phosphates as well?

Am just trying to get a clearer idea of your particular situation and method of maintaining an available P/N balance in a healthy SPS dominant tank versus a skimmerless approach that hope to allow a mature tank find it's own balance.

I've been employing a skimmer on my 120g primarily for oxidation/CO2 reduction based on the findings in this article: http://reefkeeping.com/issues/2005-08/eb/index.php

And, while I'm drawn to the idea of skimmerless for the purpose of having one less piece of equipment to maintain, I didn't realize a skimmer could have a significant impact on P reduction as compared to N reduction.

This could be one more ... or less reason to consider using, or not using a skimmer from my perspective.

 

[Belgian Anthias]

Your point that you need both N and P to grow organic matter is well taken. However, the numbers are not really accurate since if a tank had .25 of water level phosphate, there is a massive amount bound in the aragonite that will get released when you start to lower that water level. In the end, probably more phosphate left over even if you took the N down near zero.

Aragonite as a P reservoir should not be overlooked as an intended consequence of not exporting enough. It can take a massive amount of media down the road to get it out later.

That is correct, but it is not always available there where the action takes place. if nitrification takes place on aragonite , calcium, carbonate , minor and trace elements will be released and become available there where the action takes place. Using biofilters one is able to provide the substrate needed and manage processes as desired. if the reactions take place on a neutral base only what is available in the water can be used.
Often reactors and filters do not work as expected due to NOT respecting the basics of growth, and often wrong conclusions are made.

Because a skimmer plays and imported role for being able to respect de basics of growth, temporary, or periodic silencing the skimmer may often show what is or has been the problem.

If a skimmer is removed more growth will be possible to clear the water of nutrients left over by the skimmer and stayed unused. Depending of the feed a lot of that growth must be harvested to keep everything going, meaning active management is needed.

Active algae management, AAM, may restore the nutrient balance, even in a system using a skimmer. Macro Algae are fed a for the target nutrient modified feed medium.

Heterotrophic bacteria retrieve their carbon from braking down organic compounds, only DOC can be used. Adding carbohydrates will make it possible to compensate for the carbon used up for producing the energy needed, producing CO2, and it will limit nitrate production., it may wipe out the nitrification capacity if overdosed. To lower nutrients already present in the water column, often nitrate is the target, more carbohydrates are needed, but it will only happen untill the growth limited factor is reached, that too often is phosphate as it is considered the be the enemy and often is removed using GFO that also removes essential iron. When the nitrate level does not decent anymore due to the growth limiting factor, systems are often overdosed in an attempt to overhaul nature.
One does not need carbohydrate based products to manage the heterotrophic/ autotrophic growth ratio, the nitrate production can be managed via feeding, the protein content of the food.

During periods of increased growth supported by high nitrogen availability phosphorus starvation is considered to be the main cause of coral bleaching, also in captivity where coral growth differs from nature due to the light conditions. It is not because phosphate is available in the water column enough phosphorus can be supplied there where the action takes place at a logarithmic rate and membranes have to be penatrated. The use of nitrate as a nitrogen source slows down growth rates of organisms, limiting the risk for nutrient starvation within a coral holobiont and other organisms. Effective removal of ammonia by nitrification not only supports the carrying capacity but creates a more stable environment.

Nitrate is safely stored usable nitrogen, waiting for to be used by slower growing organisms, for restoring the balance between reducers, producers and consumers.
What is the argument of many authors for banning bio-filters? They did it based on the dogma nitrate is bad, mostly without adding references, which presupposes that they have established it themselves. Upon inquiry, this appears not to be the case.

It was confirmed by many and various studies phosphorus enrichment increases the growth and calcification rate of corals.
The dogma created around nitrate and phosphate is probably based on measurements made on bleaching reefs two decades ago. In the paper the results are published and conclusions are maid. A question not answered in the paper is if the measurements are the results of bleaching or the cause. Some authors of books and articles have made it the cause, although other research available at the time showed otherwise, which has been confirmed by recent research. ref: MB calcificatie Anthias 2020

Managing a closed marine system using active biofiltration is much easier if no skimmer is used. Supporting a very high bioload is made possible. No problem to keep filter feeders needing particulate organics.

 

[HuduVudu]

healthy SPS dominant tank

This is the flaw in your thinking. It is also the nuance that @jda is trying to point out. Read the link I posted. Pay particular attention to the interaction between thules and jda. Thules has a healthy SPS dominant tank. Jda points out that though it is SPS dominant and it is healthy there are certian corals that Thules can not grow. Jda's approach allows him to keep those corals. You have to ask yourself if you want to grow the corals that Jda is growing. Also know that this is just one piece of the puzzle and just because you implement this piece doesn't mean that you will be able to do what Jda is doing.