My nitrates are slowly killing my corals I have 3 Trachy's and a bunch of other LPS corals which are slowly starting to show skeletons and my Nitrates are sitting at around 40-50ppm (red sea test kit) on my Waterbox 130.4.
Phosphate reads 0-2ppb on my Hanna ULR
I assume no phosphate remover is or was used.
High nitrate availability and very ( too?) low phosphates. It has been shown that this may be a situation that may be responsible for coral bleaching at increased growth rates. In an aquarium growth often is influenced by temperature changes ( day and night, light on or of), the availability of organic carbon ( DOC and TOC), and the nitrogen source used for metabolism. Organisms grow a lot faster ( +-5x) using ammonium as a nitrogen source. Most bacteria will not make use of nitrate-nitrogen if ammonium is available. Often an increasing nitrate level is a messenger for something that may be wrong and is not the cause of the problem. The nutrient level and availability where the action is are not always the same.
At a 0 level a lot of nitrates may be produced and used. It is when a level increases one becomes alarmed and often the level is blamed instead of looking for what has caused the level to increase. On the other hand, 0 nitrates may also mean no nitrate is produced and for me that is a more worrying situation as what is considered to be a high nitrate level.
To remove nitrate due to assimilation ( algae) also phosphorus and other essential building materials are needed. If only nitrate and phosphate are used as a reference for nitrogen and phosphorus availability this would be in weight at least 10/1. Theoretically, 5ppm phosphate is needed to assimilate 50 ppm nitrate. But that is not what happens in practice.
Organisms prefer ammonia as a nitrogen source, not nitrate. As the system was overfed a lot of ammonia was produced during a period of time, producing a lot of nitrates that were not used due to ammonium availability. At the same time, a skimmer constantly removes building materials but leaving inorganics as nitrate behind creating an unbalance in nutrient availability. Also, the mechanical filter removes organic building materials that are not remineralized when cleaned in time, leaving dissolved inorganic compounds in the water. To remove those inorganic nutrients essential building materials are needed!
An algae scrubber can be used to restore the nutrient balance by feeding it with for nitrogen modified F2 media, this way everything for growth is provided exempt nitrogen which must be retrieved from the water.
For this, a small algae filter will not be sufficient as a lot of algae must be harvested to remove 40 ppm of nitrate-nitrogen. I may advise using a refuge, which makes the removal rate active manageable. \
In high nutrient systems ( high bio-load) with a skimmer, BADES can be used to restore the nutrient balance and remove nitrate as nitrogen gas.
The first thing I would check is for temperature fluctuations in the system. Then look into the nutrient situation. It may help to manage the removal rate of the skimmer and or mechanical filter.
