All plant life removes Nitrates as they use it as a food source. However, mangroves do not remove nitrates unless there are many of them in the refugium. Currently I have 18 running in my refugium and my nitrates are a Perfect zero and I feed very heavily. Mangrove leaves need to be above the water table and make sure that saltcreep does not buld up on leaves. Do not place the roots in the mud or sand for a few weeks so that they can grow and expand a bit. Mangroves have a need for magnesium so magnesium additives such as TECH M is needed. THey do need light as well as they are a plant and they can be housed in any setup.