What is a "Carbon-Limited" aquarium?

[Dom]

So I have my newest tank which has been up and running 160 days today. The tank is 125 gallons and the sump holds approximately 15 gallons for a total capacity of 140 gallons.

When testing, there are no detectable nitrate levels in the tank. And while I can understand the lack of nitrate in a new tank, I would think a tank that is over 4 months would have some nitrates.

Admittedly, there are only two Ocellaris clowns in this tank at the moment, so I can understand that it will take a lot of time to have them dirty up the tank enough to detect nitrates.

I've removed all mechanical filtration and the protein skimmer is off. But what little nitrate there is in the tank is being consumed by small algae patches by the overflow.

I want to get my nitrates up to about 5ppm because my Anemones in this tank are not inflating. They look healthy, but they just don't fill up. In comparison, the Anemones in another tank whose Nitrates are 20ppm are full to the size of a softball.

So, to increase my nitrates (and hopefully see an improvement not only in the Anemones, but in the overall appearance of my corals in the tank), I've purchased this:

https://www.bulkreefsupply.com/neon...D=4575&indexName=brs_prod_m2_default_products

Based on a 140 gallon volume and using the formula on the bottle:

(140 gallons) x (0.5) x (.1261) = 8.827 ml of supplement.

But they go on to say that if after supplementation, there are no detectable nitrates, the aquarium may be "carbon limited". What does that mean and how can I correct it; vodka?

 

[AC1211]

I had the same issue. Except I then added too many fish thinking it would correct the problem and it made it much worse in terms of algae. Most corals cannot outcompete most pest algae without the help of a clean up crew. My guess is in your case that more critters both cleanup crew and fish would be helpful.

 

[billyocean]

I have a 125 gallon aquarium and a 30 gallon sump. The sump is about half so 15 gallons...with rock and sand weight my tank volume is closer to 95/100. I treat the actual volume at about 110 gallons.

 

[ReefGeezer]

Hobby grade products like NeoNitro are pretty dilute. It always seems that it takes a LOT more to raise nitrates than the directions state. With just two fish in that great big tank, you may just simply not have enough input of ammonia or organic carbon from the foods you feed. If you think that is true, you can target feed your anemones with something like Red Sea Reef Energy AB+ or some chunky food like fish or shrimp. That provides organic carbon and nitrogen to the anemones and the system.

 

[bushdoc]

Easiest way to increase Nitrates in a tank is to increase bio load. Two Ocellaris in 140 gal tank is practically no bio load at all.
Possibly you have some denitrification going deep insifde your rocks. Do you have Bio-Blocks, especially large ones?
Besides, in a newly established Reef Tank there is little stability, so parameters are going to fluctuate. I started my 120 gal Sept 2022 and initially Nitrates were up, then down to zero, so I started to dose and now they are around 10 ppm without dosing.
I would just take a deep breath and slowly start to populate tank with more fish and some easy corals if you desire so.
Word of caution about Carbon Dosing ( Vodka, vinegar, proprietary solution)-it primarily decreases Nitrates and it is also very easy to overdo with some unwanted effects. I think it is a bit too early for that.

 

[jda]

If your tanks is even somewhat mature, having nitrate near zero is usually because of anaerobic bacteria. It is not a sign of total nitrogen in the tank. If you want the tank to have more available nitrogen to your anemones, then adding ammonium or getting more fish is likely far better than adding nitrate. However, if they look good, then they are probably fine.

Please don't look to brightwell for any kind of advice. If you dose and the nitrate go away, it is because you have anaerobic bacteria, macro or some sort of consumer. I don't even know what "carbon limited" means, but in most cases, when you add more carbon, the quickest things to react are bacteria which take up much nitrate in the process. This is a dumb statement, but them, IMO.

 

[Randy Holmes-Farley]

There is a bunch of nonsense in the reef supplement world, such as by Brightwell, about carbon limitation.

A normal reef tank is always carbon limited. You do not want it otherwise.

All it means is that if you add readily metabolized organic matter (like vinegar or vodka or sugar) to a reef tank, bacteria can eat it and grow.

 

[Dom]

Thank you everyone for the extensive and detailed replies.

I'm not big on bottled solutions. And yes, increasing the bio load by increasing the fish population is my long term plan. But I thought that adding this supplement would be a good way to bridge the gap.

If I purchased the fish today, I quarantine 90 days, so it would still be 3 months before they are added to the tank. Not to mention how long the added fish will take to bring up the Nitrates.

 

[billyocean]

Thank you everyone for the extensive and detailed replies.

I'm not big on bottled solutions. And yes, increasing the bio load by increasing the fish population is my long term plan. But I thought that adding this supplement would be a good way to bridge the gap.

If I purchased the fish today, I quarantine 90 days, so it would still be 3 months before they are added to the tank. Not to mention how long the added fish will take to bring up the Nitrates.

You can mix your own nitrate supplement for cheap as well. I have used neonitro and it was fine..just expensive in comparison. Loudwolf calcium nitrate works well.

 

[Dan_P]

When testing, there are no detectable nitrate levels in the tank. And while I can understand the lack of nitrate in a new tank, I would think a tank that is over 4 months would have some nitrates.

The explanation for your situation is simple. Algae.

Even though you do not see an infestation, there can be enough micro algae in your brightly lit aquarium to mop up all the nitrogen that the heterotrophic bacteria do not need for biomass.

 

[Dom]

The explanation for your situation is simple. Algae.

Even though you do not see an infestation, there can be enough micro algae in your brightly lit aquarium to mop up all the nitrogen that the heterotrophic bacteria do not need for biomass.

There is no algae in the tank with the exception of 3 patches of algae on the overflow box, each of which is about the size of a quarter. Is that enough?

I'm running Hydra 32s at 60%. Should I reduce the light intensity?

 

[Dan_P]

There is no algae in the tank with the exception of 3 patches of algae on the overflow box, each of which is about the size of a quarter. Is that enough?

I'm running Hydra 32s at 60%. Should I reduce the light intensity?

Micro algae including diatoms, dinoflagellates and cyanobacteria (not really an algae) are very likely happily sopping up nitrogen, existing at numbers levels that are not visible to the naked eye.

Reducing light levels is a clever response but maybe won’t be good for coral. If you believe that your water should contain nitrate, the most straightforward approach is adding food grade sodium nitrate. I am not a fan of overfeeding to raise the nitrate level because you are adding excess organic garbage to the aquarium to indirectly increase nitrate.