Cardinal Tetras Getting Aggressive?

[pinsonpa]

I have a 10 gallon with 6 Cardinal Tetras and 4 amano shrimp. The tank is cycled/established (ammonia & Nitrites = 0 and Nitrates = 5ppm). All has been fine over the last 4 weeks that I've had them.

However, over the last few days I've noticed some signs of aggression. They'll all be swimming at a regular, relaxed pace and one will take off in a sprint and chase one of the others. I can't tell if it's the same one chasing (or being chased) each time as they are pretty difficult to tell apart. I wondered if I wasn't feeding them enough but have noticed the same activity just minutes after a feeding as well. I don't see any nipped fins or anything so I don't think actuall contact is happening...just chasing as far as I can tell.

I'm using TetraMin Pro "crisps". They're pretty big flakes/crisps for such little mouths so I usually take one crisp per fish and break them up into little pieces. If all of the food is eaten within a minute or two then I sometimes add a few more crisps (broken up). Ususally this means a some tidbits make it to the substrate for the shrimp to get.

I've also noticed that 2 of the 6 Cardinals are starting to get plump bellies. Am I over (or under) feeding? I know my tank isn't condusive for breeding Tetras (most aren't) but is it possible that one or two of them are pregnant?

Maybe this normal for tetras, but I know I haven't seen any of this type of activity from them until now. All six tetras were purchased from the same tank (at my lfs) and introduced to my tank on the same day (about 4 weeks ago). The shrimp were just added 1.5 weeks ago.

Any ideas as to what's going on with George, George, George, George, George and George?

[Fishalicious]

George, George, George ..... oh heck.. you know who I mean LOL are showing common tetra playful behaviour... they are settled now.. feeling at home and giving each other a little bit of a chase around. Cardinals & Neons do this a lot... breathe easy... they are healthy little fish

Plumper Cardinals can be eggbound (females)... they will scatter the eggs and eat them faster than they can hit the substrate usually ... not something that people witness often but I know what they are upto at lights out ;) ;) Cardinals are difficult to breed so I wouldn't hold my breathe for any baby George's soon

[LosC]

My Neons do the same and are looking the same, plump. It's normal and a good sign.

[pinsonpa]

Whew...thank you both, that is a load off my mind.