Hi

,
Loaches.....This can be done.
I put three clown loaches in with my Mbuna, however I have decided that I am moving them out. The only reason for this is because of feeding difficulties......Mbuna eat a strictly vegetarian diet, whereas Clown loaches are carnivores and need a decent supplement of meaty/fatty foods (bloodworm etc.) If the Mbuna were to eat any of this regularly they would no doubt end up with the infamous Malawi Bloat and die. I therefore felt it not fair to deprive the loaches of their staple diet nor put the Mbuna at risk of Bloat.
Cories.....No.
Cories are a smaller fish and no doubt will end up being be bullied to death by the larger, more aggressive Mbuna.
Pictus.....can be done.
The only thing I would say about this is, firstly, your Labs will have to be of a fair size (3" +) before you can put Pictus in. Pictus are predatory and will eat any fish small enough to fit into their mouths.
Secondly, if your Labs are at a large enough size, I would get at least 3 pictus. They prefer to be in groups.
May I suggest (which is what I a now going to go with) Synodontis Mulitpuctatus (sp?), otherwise known as cuckoo catfish. These are very often kept happily with Mbuna but again should be kept in groups of at least 3.
Obviously, all of the above is dependant on the size of your tank. 29 gallon is not huge but should happily house your 6 yellow labs and 3 of either the loaches, pictus or multis.
Hope this helps.
steve
8)