Well you could put 30 in there but if I were you I'd get a bottom feeder of some kind to "clean up" all the stray food. Corie Cats are a good bottom feeder. If you want a loach the yoyo loach stays pretty small, as do Zebra Loaches.
thanks guys, currently there are 2 Juwel cichlids in there but they dont seem to be very happy so they are going back to the shop. You really think 30 guppies? That would look pretty cool, loads and loads of pretty colours swimming around. could i possible have 20 guppies and 2 yoyo loaches?
I'm sure you could easily do that. Just remember... 20 guppies will mulitply... those females will be pregnant all the time. If you have a second tank you could fish out the babies and put them in a smaller tank to sell once they are older.
I wouldn't worry to much about them breeding like crazy. I mean they will but the yoyo loaches will probably eat most of the fry and then the rest of the guppies will probably eat the rest.