need a cat for new cichlid tank

[Scotty]

This is really not true. Syno. eupterus, multipunctatus, ocellifer, and many of the other multipunctatus types get too large for this tank. Those that are more like S. eupterus or ocellifer may have unpleasant temperaments.
Syno. petricola, Syno. nyassae (from Malawi) or Syno. nigriventris would be much better choices. They're smaller and not as aggressive the ones previously mentioned.

I have a petricola and multiplunctatus in a tank, a fairly large ocellifer in another tank and then two eupterus in a third tank and believe me they can look after themselves but they are not at all aggressive. I also have a blue botia in with the ocellifer and a clown loach in the first tank mentioned. These fish can also fend for themselves if need be. Do remeber that a fish will grow according to the tank size and the amount of food it gets.
When looking to buy any of the Synodontis species I would recommend you try and buy as small a fish as possible and let them grow into the tank you have. This will allow you time to eventually obtain another larger tank to transfer them into at a later stage.

 

[straitjacketstar]

Do remeber that a fish will grow according to the tank size and the amount of food it gets.

This is one of the loads on BS that does not need to be fed to someone seeking reliable info. Stuffing a fish that should grow to at least 6" into a 30gl tank and later claim that it's fine cause it reached only 4 or so inches is called stunting. 8 and 10" eupterus aren't too common but not unheard of.
A fish should be properly fed in whatever tank size they are in.

You may not think they're very aggressive but plenty of other people wouldn't agree, myself included. You're fish happen to tolerate eachoher. Lucky you. Other people get lucky too but it's not always the case. I happen to have a puffer that doesn't care to rip it's tankmates to shreds like other puffers. Exception. Not the rule.
Large Synos are popular in African tanks because they can take care of themselves very well with these generally more aggressive fish. Because they themselves are territorial and aggressive. Many people cannot keep the eupterus or ocellifer types as pairs or trios since they are conspecifically aggressive. Singly in smaller tanks (40gls min) and groups in much large aquaria.

Both Syno. petricola and multipunctatus are more active in groups. In smaller numbers they are shy and hide a lot more than if they were in a group to feel more comfortable but multi's grow to twice the size of petricola.

Simple as it is, we're talking about a 30gl tank that will be home to several Aulonocara which will grow to at least 4" each. Smaller would definitely be better in this situation as there is no specification as to which species of peacock will be housed in the tank (which may ultimately be too large for a 30gl), filtration or water change regimen.