Hi , I have a plant tank, and have in it a range of crypts dwarf sag and a few other bits and pieces, that I set up about 6 years ago.
I used small gravel (about 3-5mm) with laterite under it and it is about 100mm deep. I think the tank is about 150 l.
I use Fluro lights and I have superb coverage and growth. I have had no probs with algae but I do get a little when the seasons change and I put this down to photoperiod or wave length changes.
I had Indian fern as a "starter" plant and in all this time even when I was using C02 I have never ever had a filter of any kind.
I have never cleaned the glass and I do a water change about 1x mth.
So how many fish well I have ottos, bristle nose's, a couple of kribs and as many guppies as have ever bred.
The heater is placed at the bottom of the tank so hot water rising generates water movement.
HTH and good luck
Navarre