Nitrates in reef tank?

[Belgian Anthias]

Cheato do not only need Nitrogen and Phosphor. Most photo-autotrophs prefer ammonium as a nitrogen source if available. Most have the enzymes to transform NO3 into usable NH3. Why the nitrate nitrogen is not used up by the photo-autotrophs already present? Answering the question will explain why the nitrate may increase and is not used up. In most cases high nitrates in relation with high phosphates show there is something with the availability of other elements. It are mostly just the messengers, not the cause.
For example, should iron be the limiting factor Cheato would only decrease the iron availability to other users including symbodinium in corals.
Do not remove Nitrate or Phosphate without asking yourself why the level is increasing.
As I mentioned, Cheato is one of the best methods to remove nutrients from the system if there is to much of all off them.
In some cases high nitrates or and phosphate is caused by the skimmer due to the continues selective removal of nutrients.
Adding a bit of modified F2 media may show what is going on. I deliberately use the words "going on" instead of "wrong".

If there is to much nitrate on just has to remove nitrate from the system, nothing else. Lowering the nitrate level based on assimilation, certainly when carbohydrates are added, needs all building materials are sufficiently available, otherwise the systems balance will completely be mixed up.

 

[Belgian Anthias]

As I know it - Chaeto has the enzyme that´s needed for conversion of NO3 into NH3/NH4. Further on - macroalgae often have the N-P ratio between 50 - 80 to 1 (50 to 80 atoms of N to 1 atom of P) IMO - a chaeto refugium would be great if you want to lower both NO3 and PO4. But as many have state in this thread - if your aquarium have no problems at all - why change and lower the nutrients. If you want to lower them - do it slowly, slowly and be sure that you do not run down to 0 PO4

Sincerely Lasse

Most photo-autotrohps are able to transform NO3 into usable NH3. The transformation uses more energy which influences the growth rate.
The transformation of NH3 into NH4 within the cell membranes is what may cause slow ammonia poisoning in living creatures. NH4 can not pass the membranes as the molecule is to big and may accumulate within the cells influencing internal pH. As far as I know, this happens when to much NH3 is available, , not when using nitrate as a nitrogen source. If it does this may explain why high nitrate levels may become toxic to some creatures and a reason to reduce the nitrate content in a system with 160ppm nitrate, even when the system is in balance.