A stupid question

[Tuna Melt]

So I struggle with keeping Nitrates up. My Phosphates yo-yo between 0.05 and 0.09, but my Nitrates are perpetually declining. I was previously dosing neo-nitro to maintain my desired level of Nitrate but I stopped because I view measured Nitrate as a representation of excess N in the system rather than a measure of true usable N. That's because corals prefer ammonia and that's their primary (preferred) source of N. I'm no expert, in fact I'm a newbie, but that's what I've heard.

So... I've been trying to increase Nitrates organically, said differently I'm trying to make sure there is enough usable N in the system by solving for a bit of excess N i.e. Nitrates. Some folks say "feed more" but even if I feed exclusively frozen my phosphates increase at least commensurately (usually more) than Nitrates. I'm happy with Phosphates and don't want them to increase. Some people suggest adding more fish, but why would that change anything, I'm still adding the same ratio of N&P into the system in from the additional food.

So my question is, does adding a fish increase nitrates in relation to Phosphates? Or does it increase both proportionately?

I guess if fish metabolize at a higher ratio of P/N than the rest of the tank they could? Like if a coral consumes 10N for every 1P, or algea consumes 16N for every 1P, do fish consume 5N to every 1P so adding another fish decreases the average ratio of P/N consumption?

Another random rambling thought which kind of answers the above question - a quick google search suggests that animals have a much lower N/P ratio than plants ~(8/1 vs 15/1), so maybe I could drop some nori in more frequently? My only herbivore is a tailspot blenny but it may be worth a shot. This could also help explain my issue since my primary export is an algae scrubber which is consuming N/P at a 15/1 rate...

Anyway, those are my rambling thoughts, thanks for bearing with me!!

 

[Rick's Reviews]

@Randy Holmes-Farley

 

[Randy Holmes-Farley]

I do not know if ammonia uptake by corals gives appreciably different results than nitrate uptake (there’s very little evidence on that) but if it concerns you, you can dose ammonia. There is a diy recipe thread.

 

[Randy Holmes-Farley]

DIY Ammonia dosing for low nitrate systems

Some reef aquaria have chronic low nitrogen availability. One indicator is very low nitrate. Nitrate dosing is a fine remedy, but it is possible that ammonia dosing may be more beneficial for some organisms since ammonia can be energetically easier to assimilate than is nitrate. For this...

www.reef2reef.com

 

[jda]

You likely are in a place where your ecosystem has developed a good population of anoxic bacteria. These bacteria live where there is little/no oxygen and turn no3 into N gas. This completes the nitrogen cycle. This will usually keep just a trace of no3 in tanks where this happens - like "clear" on most test kits, but actually like .1 to .5 if you can be more precise.

Adding more nitrate will usually only grow the population of these bacteria and you will still be very low.

There is no process like this for po4, which is why the po4 rises and the no3 declines.

Tanks have been like this since the DSB days. It is no issue if you are feeding well and stuff. I have no3 at .1 but I feed a lot - there are tank photos and stuff in my tank thread.

 

[Tuna Melt]

You likely are in a place where your ecosystem has developed a good population of anoxic bacteria. These bacteria live where there is little/no oxygen and turn no3 into N gas. This completes the nitrogen cycle. This will usually keep just a trace of no3 in tanks where this happens - like "clear" on most test kits, but actually like .1 to .5 if you can be more precise.

Adding more nitrate will usually only grow the population of these bacteria and you will still be very low.

There is no process like this for po4, which is why the po4 rises and the no3 declines.

Tanks have been like this since the DSB days. It is no issue if you are feeding well and stuff. I have no3 at .1 but I feed a lot - there are tank photos and stuff in my tank thread.

Thanks for the responses! I do have a 1.5-2 inch sand bed but I think it is decently aerated, a few conches, a sand sifting starfish, and some nassarius snails. I'm not sure I have many anaerobic spots in my system.

DIY Ammonia dosing for low nitrate systems

Some reef aquaria have chronic low nitrogen availability. One indicator is very low nitrate. Nitrate dosing is a fine remedy, but it is possible that ammonia dosing may be more beneficial for some organisms since ammonia can be energetically easier to assimilate than is nitrate. For this...

www.reef2reef.com

Thanks Randy, I was hoping to accomplish my goals through a more natural means if possible. It would be much easier to add another fish or throw in a sheet of nori every few days than carefully dosing ammonia? Do you think there is any merit to this?

So my question is, does adding a fish increase nitrates in relation to Phosphates? Or does it increase both proportionately?

I guess if fish metabolize at a higher ratio of P/N than the rest of the tank they could? Like if a coral consumes 10N for every 1P, or algea consumes 16N for every 1P, do fish consume 5N to every 1P so adding another fish decreases the average ratio of P/N consumption?

Another random rambling thought which kind of answers the above question - a quick google search suggests that animals have a much lower N/P ratio than plants ~(8/1 vs 15/1), so maybe I could drop some nori in more frequently? My only herbivore is a tailspot blenny but it may be worth a shot. This could also help explain my issue since my primary export is an algae scrubber which is consuming N/P at a 15/1 rate...

 

[Jasonak]

I had similar problem, I removed all my caulerpa from my sump now ive got phos and Nit.

 

[jda]

If you have sand that is a few months old, or older, your nitrates are low or falling, and your po4 is climbing then you almost certainly have enough anoxic zones.

If you up your feeding, get another fish, etc. and the no3 does not rise, then this for-sure is denitrification through bacteria. Again, if you are feeding well, then this is not a problem - if it is, I have not seen it. The worst thing about having low no3 is that the coralline grows so fast that I get sick of scraping it.

 

[Tuna Melt]

If you have sand that is a few months old, or older, your nitrates are low or falling, and your po4 is climbing then you almost certainly have enough anoxic zones.

If you up your feeding, get another fish, etc. and the no3 does not rise, then this for-sure is denitrification through bacteria. Again, if you are feeding well, then this is not a problem - if it is, I have not seen it. The worst thing about having low no3 is that the coralline grows so fast that I get sick of scraping it.

So after pondering this for months I think you’re right. What baffles me is that my sand bed is not that deep. I’m thinking of slowly siphoning the sand out until the nitrates climb to a place I’m happy with (10 PPM).

The reason I am totally convinced I have denitrifying bacteria somewhere is because when I dosed CIPRO to stop a coral pathogen my nitrates spiked after months of struggling to raise them. Even dosing 10 ML of NeoNitro per day could barely raise em. The Tank was started at the end of Feb 2023 so this is representative of the nitrate level for the whole life of the tank (sorry for the quality, lol). I started dosing NeoNitro in Aug, hence the little spike, and did the Cipro treatment in October, just prior to the big spike:

 

[jda]

I do not think that it is possible to try and add/remove sand to hit a nitrate reading. The bacteria can become so emmense in a small area, that they will either have enough room to multiply as the fuel allows, or there is so little sand that it is oxygenated all of the time and the anoxic bacteria cannot grow.

In 30 years, I have never seen a single case where anybody could control this outcome.

 

[Tuna Melt]

I do not think that it is possible to try and add/remove sand to hit a nitrate reading. The bacteria can become so emmense in a small area, that they will either have enough room to multiply as the fuel allows, or there is so little sand that it is oxygenated all of the time and the anoxic bacteria cannot grow.

In 30 years, I have never seen a single case where anybody could control this outcome.

Thanks, that was exactly the feedback I was looking for! Question now becomes, do I unleash the nitrate beast

 

[jda]

Why would you want your corals to get nitrogen from nitrate instead of ammonia and nitrite?

Most of the best tanks on the planet have incredibly high input and also incredibly high export with low residuals.

IMO, having a sandbed that keep no3 with just a trace is a blessing.

 

[Tuna Melt]

Why would you want your corals to get nitrogen from nitrate instead of ammonia and nitrite?

Most of the best tanks on the planet have incredibly high input and also incredibly high export with low residuals.

IMO, having a sandbed that keep no3 with just a trace is a blessing.

Well I would love for them to get all the N required from ammonia and nitrite, but I doubt they do even with my surplus of fish. This means they are N limited in my current system that has no nitrate for them to uptake when ammonia and nitrite aren't available. I can't feed more to get the N up because my po4 will fall out of balance.

Now I'm assuming reef tanks are generally N limited (if they have no measurable nitrates) because most "experts" I've heard opine on Nitrate levels recommend 5-10 ppm (or 100x po4). Meaning they have seen better results with a surplus of nitrate. If that wasn't the case I guess why did we move away from targeting zero nitrate and the DSB days?

*Cavate* I know conventional wisdom (specifically in this hobby) can be totally wrong, i.e. the DSB days were wrong per today's standards. And I know that we don't really know, so why try for something that may be wrong?.. But I think trying for the best practices (even if its wrong) is better than not trying for something just because the best practice could be wrong. But that being said, I don't know, maybe its really not that important

 

[jda]

IMO, having nitrate is only a sign that you MIGHT have an excess of nitrogen - even if so, you have no idea if it is available for everything to use. Not having nitrate is a sign of nothing for sure.

Since there are biological processes in the tank that can turn no3 into N gas, you can have an excess of nitrogen sources for your corals and the residual levels be very low. Also, not all corals can use nitrate and those that can have to turn it back into ammonia/ammonium for the symbionts to use which costs an estimated 30-70% of additional energy (nobody knows for sure) - not all corals have this kind of energy to use which is why they can die in high no3 systems without much ammonia, IMO.

Some of this is a matter of knowledge and faith. Knowing that ammonia and then nitrite are easier or any coral to use. Knowing that having a surplus of trash is no indication that people ate well (bad false-equivalency).... or that no trash does not mean that people starved. All live tissue can suffer as waste products increase to varying levels. The high energy cost of using nitrate to get nitrogen for corals. People base the foundation of their lives on a faith, so this should not be so hard.

Check out my tank thread and see what feeding a lot of fish and also exporting a lot can do. I buy frozen food by the kilo (photos in there that are kinda fun), pellets by the 5lb and feed 12-15 larger and countless smaller fish enough to grow and not be aggressive (like 10x tanks all getting along). In all of the years, this is what I have found to be best for nitrogen.

Phosphate accumulation is a bit harder since there is not equivalent to a sandbed. As a general rule, if phosphate is accumulating, then you are not likely limited on nitrogen since they kinda come in together.

 

[Randy Holmes-Farley]

IMO, having detectable nitrate is a sign that you do not have a deficiency of N. It could also be that having more ammonia and less nitrate might (or might not) be better.

 

[twentyleagues]

So here is other stupid questions. Are your corals suffering? Is there a lack of growth? If so is the lack of growth related to low nitrate and not light or flow?