Keyhole Cichlids Aggression?

Question
Hi!
We've had a tank for several years now and about 6 months ago, after losing several fish we added 2 Keyhole Cichlids.  Nothing much happened with them - they're simply bonny to watch.  They've increased in size and apart from the odd chase around the tank they are quite passive.

Today however, we added 2 convicts (were told a male and female) and replaced a few plants.  Within 10 minutes of this the 2 keyholes are kissing/locking jaws.  We are assuming that this is aggression not mating, although we had thought that we had a male and female.  Any thoughts? Are they likely to damage one another?  The convicts seem pretty ok - no aggression but at the same time not paying much attention to one another either....
Thanks
Kirsteen

Answer
Hi Kirsteen;

They may be responding to the extra population by fighting. Keyholes usually pick their own mates so even if you are sure you have a pair, maybe they don't like each other?

The real problem you will have soon is when those convicts begin to spawn. They are very, VERY aggressive when guarding their nest and have been known to kill fish 3 times their size to do it, or die trying. I fear for your poor little keyholes. They will probably be killed. They really are better off without the convicts in with them. The convicts will do well in a 20 gallon or larger of their own with no other fish, but you should be sure you have a new home for the babies. Convicts are pretty prolific and for fish stores to take the babies they have to be grown big enough. Just something to think about.

At Your Service;
Chris Robbins