What has not been mentioned (I think) is lighting levels and max or min temperatures you may be able or want to provide. There is a big difference is what fish and plants need in general. Shade loving plants are much easier to accommodate. I grew selaginella without supplementary lighting, in a very large laboratory desiccator for some years until it hit the roof, so to speak, and have had Pinguicula (moranensis?) with Utricularia alpina in an old fish tank for close to 20 years, potted not planted out, with no more lighting than a 20 watt compact fluorescent, but the lamp is just inches from the plants and not really quite enough. The latter was used for 15 years as a "security" light in a house that was unoccupied much of the time, when I worked away from home. The theory being if I was to have a light going on and off with a time switch it might as well have plants under it. I haven't had the heart to break it up yet after such good service The Pinguiculas are ~8" across and the Utricularia flowers for much of the year, but the tank does not look to pretty after all this time. Just rain water every few weeks. Brian Whyer, Buckinghamshire, England, zone ~8