The problem with both linked charts is that they can only be very general. It is impossible to factor in all the variables.
Fish compatibility has to do not only with behaviours and numbers. The influencing factors include:
Tank size: first, water volume [many only think this when considering tank size]; second, its shape (whether it is a long or tall--a 20g long can house more fish than a 20g tall, and/or will be more or less suitable, depending upon species).
Filtration: not all fish will be "OK" with any filter, especially the water movement. Stress and even death can occur if filtration is not suited to the fish species.
Tank Environment: plants, wood, or rock are needed by some fish.
Light: Most fish need minimal lighting [floating ploants can achieve this], some need near-darkness.
Water parameters: temperature, hardness and pH. As one example, not all rasbora have equal requirements, yet they are indicated as compatible in those charts.
Behaviour: probably the best understood in most cases, but as the above hopefully shows, only one factor of several.
In my 20 years experience, the only way to assess true compatibility is to research each species and see what it requires in terms of the above factors. And these are all included in our profiles.
Last edited by Byron; 10-22-2011 at 01:13 PM..