Slow coral growth with lower nitrates

Jonathan lee · Apr 25, 2023

Hi, recently my tank has been running with lower nitrates as before and one major thing i realised was slower coral growth and they aren’t as puffy. I only keep lps and softies and they both have slowed down in growth ever since my nitrates dropped to 5. I used to run my tank with high nitrates 40-50(lfs said corals would love it at 40 too lol) and the corals were growing faster. But now with nitrates only at 5 they have barely grown albeit still growing just not as fast as before. Why is that? 5 isnt that low tho and should be fine, no? Neon hairy mushrooms even started to bleach a little and have stopped growing big and splitting. All the favias growth slowed down, gsp on back wall growing ALOT slower, candy cane not splitting for months now when it used to split quite often, duncan has stopped producing heads too when it was the most prolific grower, frogspawn and hammer slowed down too. The babies coming out from the skeleton just stopped growing bigger.

Crustaceon · Apr 25, 2023

Jonathan lee said:
Hi, recently my tank has been running with lower nitrates as before and one major thing i realised was slower coral growth and they aren’t as puffy. I only keep lps and softies and they both have slowed down in growth ever since my nitrates dropped to 5. I used to run my tank with high nitrates 40-50(lfs said corals would love it at 40 too lol) and the corals were growing faster. But now with nitrates only at 5 they have barely grown albeit still growing just not as fast as before. Why is that? 5 isnt that low tho and should be fine, no? Neon hairy mushrooms even started to bleach a little and have stopped growing big and splitting. All the favias growth slowed down, gsp on back wall growing ALOT slower, candy cane not splitting for months now when it used to split quite often, duncan has stopped producing heads too when it was the most prolific grower, frogspawn and hammer slowed down too. The babies coming out from the skeleton just stopped growing bigger.

Ok, so raise it back up to 40-50. Ignore posted parameter recommendations if you're tank is doing well with your current parameters.

JCM · Apr 25, 2023

Unlikely it's actually the nitrates causing the issue. What your test kit is reading is the excess in the water. Having any excess in the water means the inhabitants aren't limited.

homer1475 · Apr 25, 2023

Better question would be how fast did you drop the nutrients, and with what method? You could be bottoming out your phosphates depending on the method used for nitrate removal.

Could also be the corals just adjusting to the lower nutrient levels depending on fast you dropped them.

Jonathan lee · Apr 25, 2023

homer1475 said:
Better question would be how fast did you drop the nutrients, and with what method? You could be bottoming out your phosphates depending on the method used for nitrate removal.

Could also be the corals just adjusting to the lower nutrient levels depending on fast you dropped them.

I dont know how fast it dropped. Basically i made a small change in the baffles in the sump so water would flow through the media better and one day the nitrates were 20 then now 5. But i dont know the span of time it took to drop. There was a few months where i didnt test nitrate so i dont know how steady the drop was. I think i did bottom out at some point causing some imbalance cause for I suddenly had red slime outbreak which still isn’t fixed yet