wellll...... if i were you, i would take back the shark, it gets far too big to comfortably house in a tank under 55-75g and even less so concerning water quality with so many other fish in there.
id also really consider picking a hard water/high pH tank or a soft water/low pH tank (depending on your water source) and stick with it. danios/angels/cory cats are all softer water/lower pH fish where as your platies really prefer hard water with a touch of salt in the water to even as much as a brackish system.
im not sure if you have 'too many fish' if you remove the shark but you have wildly different water quality requirements. if you want to keep the angel instead, take away the platies and the shark and add some more cory cats (4-5). they get quite playful when they have more brothers and sisters around.
try to stick with the same kind of cory cat though.
EDIT- i wouldnt add anythign else to the 2.5 housing a betta than shrimp. everythign else takes up too much space or territory.
Chris- Husband, 04/30/77
Cailyn- Daughter, 07/05/99
Jeffrey- Son, 03/24/06
Alex- Son, 03/25/09
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Last edited by want4rain; March 15th, 2008 at 09:12 AM.
Reason: whoops! forgot to add...