Are any of the South American cichlids suitable for a 20 gallon long?Ive seen some people keep black convicts in a 20 gallon but they seem to get too big for it.Im realy not into the rams that much im looking for something more hardy and forgiving since this is my first aquarium in 10+ years.I tetsted my tap water and the GH is around 25,KH close to 0 and PH around 6.5