Carbon dosing confusion

carri10 · May 28, 2023

Hello All.
I am in the process of designing my tank. It's going to be an approx. 250 gallons, 1000L system, with a basement sump etc.
I was going to go with a std (I think Berlin type) set up of some filter socks or equivalent, followed by some intermitant skimming and a large refugium, with 10% / week water changes.
Fairly standard and low risk.

However, I've seen some tanks (notable @SunnyX) that run carbon dosing for nutrient export.

I fully get the advantage of bacteria in the water column as coral food (as SunnyX states) and can see how bacteria would do a good job of nutrient uptake allowing eventual export.
What I don't understand is the following:
If there is a decent amount of food going into the tank, that which is not eaten by the fish will degrade and be eaten by bacteria. Why do you need to carbon dose to boost bacteria growth? The bacteria will naturally have more than enough uneaten fish food going around to grow.
So why would carbon dosing increase growth and make bacteria available as food for corals?
Why would there be more bacterial growth allowing export via a skimmer?

Sorry if I am fundamentally missing something here. Just looking to get the simplest (KISS) and most robust method to control filtration and export in my tank. I can't argue against the results, however, some carbon dosed tanks look stunning.

As a second question, between the 2, filter/skim/refugium vs Carbon dosing, which is seen as the most robust, i.e. most reliable, least amount of dialing in, least delicate to changes and easiest to set up?

Thanks all.

Dan_P · May 28, 2023

carri10 said:
Hello All.
I am in the process of designing my tank. It's going to be an approx. 250 gallons, 1000L system, with a basement sump etc.
I was going to go with a std (I think Berlin type) set up of some filter socks or equivalent, followed by some intermitant skimming and a large refugium, with 10% / week water changes.
Fairly standard and low risk.

However, I've seen some tanks (notable @SunnyX) that run carbon dosing for nutrient export.

I fully get the advantage of bacteria in the water column as coral food (as SunnyX states) and can see how bacteria would do a good job of nutrient uptake allowing eventual export.
What I don't understand is the following:
If there is a decent amount of food going into the tank, that which is not eaten by the fish will degrade and be eaten by bacteria. Why do you need to carbon dose to boost bacteria growth? The bacteria will naturally have more than enough uneaten fish food going around to grow.
So why would carbon dosing increase growth and make bacteria available as food for corals?
Why would there be more bacterial growth allowing export via a skimmer?

Sorry if I am fundamentally missing something here. Just looking to get the simplest (KISS) and most robust method to control filtration and export in my tank. I can't argue against the results, however, some carbon dosed tanks look stunning.

As a second question, between the 2, filter/skim/refugium vs Carbon dosing, which is seen as the most robust, i.e. most reliable, least amount of dialing in, least delicate to changes and easiest to set up?

Thanks all.

Why carbon dosing is needed?

Heterotrophs use food for energy and to make new cells. Much of the food consumed goes to making energy and that means using carbon and pooping out unused phosphate and ammonia. To get rid of this unused ammonia and phosphate, one adds carbon to supply energy and get the bacteria to make more cells which uses ammonia and phosphate. What you missed is that heterotrophs use a large amount of carbon to generate energy and less for biomass or cells.

Mechanical filtration, skimming, carbon dosing, refugium/growing macro algae accomplish different things and are selected according to what water quality issue needs addressing AND what the aquarists feels like using. Often these techniques are selected for emotional reasons rather than for strictly technical reasons. For example, a refugium might seem natural whereas carbon dosing seems unnatural and using nasty chemicals.

ZoWhat · May 28, 2023

I started using this 2 years ago after watching this video.... completely changed my tank for the better

Bottomline:
* 0 nitrates and phos = bad

* Good amt of nitrates and phos = bad

* a little nitrate and phos = great

BactoBal will greatly help you walk the tightrope

bushdoc · May 28, 2023

Dan_P succintly explained how and why carbon dosing works.
I would add word of caution-carbon dosing can lead to problems, it can easily be overdosed and some reefers reported STN while dosing carbon
I would not advocate carbon dosing at the beginning of reefing career, not in new tank. Berlin method and some modification of it is a perfect starter for new , large reef tank.

carri10 · May 31, 2023

Thanks very much for the information.
I suppose the thing that I misunderstood was that the aquarium would be carbon limited.
I kind of assumed, with all of the food that was going in, carbon would not be a limited element, therefore I struggled to see how adding e.g. vinegar would make any difference.
That’s clearly wrong, because, as I have researched after your comments, it seems people even have bacterial blooms after adding extra carbon.
Good to know, and great to increase my knowledge on this subject.

Also, thanks for the advice that carbon dosing is not necessarily for beginners.

Pntbll687 · May 31, 2023

Carbon dosing on a new tank is probably not needed, as it grows in, maybe.

I carbon dose my tank using vinegar. 2 Cups vinegar mixed with 9 gallons of RODI, and 18tsp of kalkwasser mixed in one container. Calcium/Alkalinity/Carbon source in one solution, 750ml a day in my 180g system.