Nutrient management without fish

[razorskiss]

I have a 25g all invert tank that I struggle to balance nutrients in. Filtration is a canister filter with coarse sponge and some ceramic media. During the ugly phase I had added a reef glass nano skimmer and run it fairly wet for 6 hrs at night, after adding the skimmer and as the tank has matured I can't keep nitrates above 0 without dosing and phosphorus export seems nonexistent so I've had to start running GFO and occasionally dosing lanthanum to keep it to 0.1 ppm or lower.

I wonder if the ceramic biomedia has actually become too good at nitrogen fixation and the system is limited by this since, despite being completely sealed I've found that the canister will regularly blow bubbles (maybe once every few hours), maybe a sign of nitrogen gas formation in from anaerobes?

I'm tempted to try shutting off the canister filter to see if I can get better N/P balance in the system since even feeding prepared coral foods doesn't move the dial on nitrates at all and shoots phosphates through the roof. Of course doing this would probably kill the microbe population in the canister so I'm terrified of taking this step and having the tank crash.

The tank grows coralline ridiculously fast, softies and LPS generally seem happy. I have one acro that's kind of alive but no PE, a Stylo that looks reasonably happy and is encrusting (but not a lot of length growth), and a green monti digi that was growing decently but has recently lost some color (but still get some PE on it).

I feel like this N/P issue also drives a cyclical pattern of GHA / bubble algae breakouts (just got the last one under control).

Given the coralline growth I feel like on the edge of a breakthrough but I just can't figure out what to do from here...

 

[1979fishgeek]

I’m following along. I’m having similar issues in my mixed reef my nitrates just keep bottoming out, I’ve turned off my roller mat, removed the skimmer cup so it just overflows and taken out the majority of the cheato, not done a water change in 3 months and no3 has continued bottoming out, but po4 has to be controlled to keep below 0.3ppm. I even added more fish and feed really heavy, four times a day frozen, pellet foods and zooplankton based foods for coral, plus aminos. The only filter media I run is a handful of maxspect nano spheres and live rock.
My system keeps adapting to the no3 I try and add, I managed to get no3 to 5.5ppm and then it’s started dropping again despite feeding even more, I measured it tonight at 1ppm using Hanna Nitrate checker.

EDIT: I should add I’ve even tried dosing no3 and the system just absorbs it.

I too have fantastic coralline algea, a small area I’d bubble algae (which I manually remove) but my corals need better colour, they have great feeding response and PE but colours just not right.

 

[razorskiss]

The recent posts about dosing ammonia made me think to bring this up, although I'd prefer to avoid a dosing-dependent solution it doesn't seem feasible given that phosphates pile up if I try to feed coral foods heavily while any nitrogen products from the breakdown seem to get eliminated. I don't know quite enough about reef chemistry to say what's limiting the system if nitrogen gets taken up super efficiently but phosphates not at all.

 

[Dan_P]

I have a 25g all invert tank that I struggle to balance nutrients in. Filtration is a canister filter with coarse sponge and some ceramic media. During the ugly phase I had added a reef glass nano skimmer and run it fairly wet for 6 hrs at night, after adding the skimmer and as the tank has matured I can't keep nitrates above 0 without dosing and phosphorus export seems nonexistent so I've had to start running GFO and occasionally dosing lanthanum to keep it to 0.1 ppm or lower.

I wonder if the ceramic biomedia has actually become too good at nitrogen fixation and the system is limited by this since, despite being completely sealed I've found that the canister will regularly blow bubbles (maybe once every few hours), maybe a sign of nitrogen gas formation in from anaerobes?

I'm tempted to try shutting off the canister filter to see if I can get better N/P balance in the system since even feeding prepared coral foods doesn't move the dial on nitrates at all and shoots phosphates through the roof. Of course doing this would probably kill the microbe population in the canister so I'm terrified of taking this step and having the tank crash.

The tank grows coralline ridiculously fast, softies and LPS generally seem happy. I have one acro that's kind of alive but no PE, a Stylo that looks reasonably happy and is encrusting (but not a lot of length growth), and a green monti digi that was growing decently but has recently lost some color (but still get some PE on it).

I feel like this N/P issue also drives a cyclical pattern of GHA / bubble algae breakouts (just got the last one under control).

Given the coralline growth I feel like on the edge of a breakthrough but I just can't figure out what to do from here...

I am guessing you have a relatively new system that is consuming the nitrates faster than you are adding protein (fish or coral food). Everything in your system is removing nitrogen. Your choice is to add more nitrogen or start removing things.

A minimal risk removal is to start slowly removing ceramic medium. Your sand and rock will take over the job of nitrification. Go slow because you might hit a tipping point where nitrate will start to accumulate. Cleaning the sponge filter more often will keep bacteria activity lower but I don’t know whether that will have a noticeable effect on nitrogen consumption. Safe enough to try. Then there is the option to add nitrate to the water in the form of food grade sodium nitrate. I am not a fan of adding more food to the tank because that also adds more phosphate and organic garbage that might fuel nuisance organism growth.

 

[razorskiss]

I am guessing you have a relatively new system that is consuming the nitrates faster than you are adding protein (fish or coral food). Everything in your system is removing nitrogen. Your choice is to add more nitrogen or start removing things.

A minimal risk removal is to start slowly removing ceramic medium. Your sand and rock will take over the job of nitrification. Go slow because you might hit a tipping point where nitrate will start to accumulate. Cleaning the sponge filter more often will keep bacteria activity lower but I don’t know whether that will have a noticeable effect on nitrogen consumption. Safe enough to try. Then there is the option to add nitrate to the water in the form of food grade sodium nitrate. I am not a fan of adding more food to the tank because that also adds more phosphate and organic garbage that might fuel nuisance organism growth.

My system is about 10 months old at this point. Good point about the media, I'll try removing some of it.