Hi all,
I'm going to tell you plants are the answer.
I understand it is difficult with herbivorous fish, like
Tropheus, but that is the great advantage of plants, they are very efficient at depleting fixed nitrogen, and you get a <"
visible indication of nutrient content">. When you harvest the plants that nitrogen (and <"
all the other nutrients">) are removed.
Planted tank keepers have to continually add nitrate, mainly due to their relatively light stocking densities and heavy planting, but in <"
aquaponic systems plants will still deplete nitrogen levels">. Most fish-keeping literature and forums vastly underestimate the nitrogen removal potential of plants, particularly floating or emergent ones.
<"
Anion selective resins work">, but you have to keep on testing for nitrate (NO3-), to tell when the resin is exhausted, <"
which isn't entirely straightforward"> and <"
there is the cost issue"> when you treat a large volume of water which has relatively high NO3- levels.
cheers Darrel