Does the betta eat them? My male betta ate a few of mine 3 out of 5 that we had in a 10 gallon. I am sure 8 in a 2 gallon is better than at the LFS when they have like 1000 in a 10 gallon. They CAN get up to 2 inches each, but mine are both under an inch and I've had them for awhile. Now I am only down to one as my male betta got hungry again. I moved the last ghost shrimp into my 120 gallon and now I can't even find him. I am going to go get some more today.
Oh, my Male-Betta is finde with the Shrimps- I count them everyday and besides extra skin I don't find any dead or fanished ones! MMh, not counting the Antenneas each of my Shrimp is about 1 cm long, not even halb a inch!
I personaly think that's too many. If you have fish, you should stick to only one shrimp to every half gallon - so 4 shrimp at most plus the betta. Shrimp do produce waste and do breathe oxygen so they should not be over-looked when it comes to bioload. Depending on the potential size of both the shrimp and fish etc, I'd alter the number but 8 seems too many for a 2 gallon with a 3 inch fish in there too.
3 inch-fish, my Betta must be young then because he's only a little over 1 inch long. But you are right! I already talked to a friend of mine who has a 10-Gallon-Tank, she'll adopt 5 of my Shrimpies! 3 I think should be fine now, right!?