Every case/tank is different.
-First I look at size. The size of the tank as well as the size of the fish. For fish under 4in I take into consideration the inch per gallon rule. For fish over 4in, I keep the inch per gal
. rule in the back of my mind, but then imagine swimming room. That gives you a rough estimate of what could go in the tank. Then add a few more fish, ha.
- I look at species. Goldfish need 10gals each as well as most species of BW puffers.
-I then look at territory. Are some of the fish going to be more aggressive towards others- do they need to have the whole upper or lower area to themselves?
- Maintence. I look at who Im talking to. If JChillin wants to "overstock" his tank slightly- he is just the man to do it right. However, if the person is relativly new, then you might want to advice a lesser stocked tank.
- I also look at other things like filters or if they have plants or not.
It's all relative. Some people have different opinions than others. Sometimes it works, sometimes it doesn't.