my sharks are acting strange!!!

I have 2 sharks 1 red tail and 1 rainbow shark. Normally they just leave each other alone. Just today i noticed they were kinda chasing each other but not in a agressive way, i wish i had a digital cam then i could have made a video for you all to see. I'll try to explain it the best i can LOL. They were chasing each other in tight circles around one area , my red tail would go on his/her side for a couple seconds while the rainbow was swimming around him/her they were doing this for a good half hour. My question is, can these two type of sharks mate? my red tail shark seems to be awefully big around the belly. could she be laying eggs??

It sounds like that's exactly what they're doing, but I can't say for sure. I believe they are a species of catfish, which are egg scatterers. In any case, the fry will not have much chance of surviving in a community tank. Google may have more information on the species.

Maybe she is laying eggs, but here is another scenario. Red tail sharks, black sharks, and rainbow sharks are all similarly shaped fish. These fish are aggressive among their own kind as well as similarly shaped fish. I know you say they are not behaving aggressively so perhaps they are indeed spawning. How big is your tank? Have you noticed them hanging out together(not chasing) or do they have territories at opposite ends of the tank? I just thought I would throw this out there just in case.

my tank is 30g.Yeah they do look more like cat fish then sharks Im gonna google it and see if maybe someone else has similar experiances. thanks for the help

They are catfish, as are most aquarium "sharks"

I had both in my 55 and they weren't fond of each other.

Neither species is easy to breed...

It would indeed be neat if that's what they were doing... but I tend to lean the way as Meg and say that they're generally aggressive to each other...

A large Red tailed shark, or a large rainbow shark are each territorial in their own right... Let alone one of each in a tank...

It is only my opinion...but from observing them in at the LFshop I've worked sometimes they do this as a submissive posture.
Your Rainbow is known to be the more aggressive of the sharks...more so than the red tail. It usually does not tolerate it's own kind..not unless you have at least six or more in the tank.
Having only one of each ( and different species)..there is going to be huge territorial disputes the more mature they become.
I know I have been saying this a bunch..but having a larger tank ( at least a 55 gal.) may be best.
Since sharks are fast moving.. schooling fish..they need lots of room.
If another gets in it's way..chasing & aggression will most likely be a common occurance. It may even get extreme.
How long have you had these?
Give it some caves and hiding places if you can.
It is "possible" that this is spawning behavior..but in honest..I doubt it.
As Angela stated..they are extremely hard to breed. Also..these are two different species of sharks..so nope..I seriously don't think so.