Originally Posted by SinCrisis
organic potting soil would indicate no additives no? Ive seen a tnak a long time ago that used soil as its substrate. It was a 15 gallon with 2 angel fish and a couple really long grass-like plants. There was no additional substrate such as a layer of gravel or sand. The tank used 1 power filter with a diverted flow so there was very little surface agitation and very little current going straight down to the bottom, im guessing most of the aeration was from inside the filter. This setup yielded clear water. so it is possible to use it as a sole substrate but special care and plaing must be used to make it work.
Well, almost anything is possible. Most of us advocate weekly partial water changes, but there are some aquarists (quite a few I understand) who never change any water, have no filters, and have (supposedly) healthy fish. I don't doubt that approach may work, but on this forum I would not suggest that approach to someone who may not have the experience to manage it properly--and for most of the time I've no idea what level of understanding others have. In another thread (or another forum maybe) someone said it was OK to maintain rift lake cichlids in a tank with acidic water at pH 6.6 and no hardness. Well, maybe his fish were healthy, maybe not. I certainly would not tell anyone to do this, in my opinion it is only asking for disaster. Not that using soil is a disaster, but what a mess in the wrong hands. And the nutrients into the water is a very real issue, according to every plant authority I've read. The person with a soil substrate will probably next be asking for help in cleaning up exploding algae.
All of us, myself included, must never forget that the fish are in a closed environment, and when we do something to any part of that system, it may, or more likely will, have an effect all along the way, and untimately to the fish. Unless one has the knowledge to know what those impacts will be, and how to deal with them, experimenting or straying from the tried and true should be done cautiously.