Hi Spazz >> Not see ya in awhile > < You cool .

Any who ... Many dif things to think of : Maitenance is easy with a Fluval type cannister filter system . Google it as to 20 gal tank . Keeps constant bio world >>> Instructions explain how >>>> Extremely low maintenance .

Lava rock bottom cover is easily filtered ,, no need for underground filter stuff with peguin type airator . { cannister airator filter system very worth the cost .}

In so far as fish go Plecostamus get along with all community and semi - aggressive fish . Pleco is an algea eater type fishy .

Schooling fish are the coolest to watch and you can put many dif species as to community classification .

The 1 fisk per gallon ??? >>> I have a 55 gal and I would be reluctant to put 55 fish in there ... Most I have done was 30 fish . Schooling groups of 5 or 7 and sometimes if tetras >>> mix them up in 3 's .... Think color and know some will die and you can rotate as you see most suited .

I have had tanks of all sizes for years >>> mollys and swordtails are pretty too .

First think of maintenace and filtration system . And then You will figure out the rest in time ...

B T W >>> Google the filter systems I suggested Fluval type cannister type are awesome .