Malawi 20

You need a much bigger tank. That stocking is pretty horrible for a 20g, I'd go at least a 55g (though the crabo really needs a 75g). They are all still babies that is why you haven't seen issues yet, but I'd bet money you're going to shortly. That water change schedule is not near enough either.

I am surprised that the Bumblebees haven't killed off any fish yet, as for they are aggressive at an early age, but yep you will most def find issues here in a month or so..

None of the fish you have listed will survive in such a small setup when grown you may get lucky and have one fish to survive the whole process and even then it will live a miserable existence, Mbuna need space and plenty of others to feel comfortable and to equal out aggression, its the nature of the beast..

Bumblebees are probably one of the most aggressive species of Mbuna you could have chosen they will need at least a 75gal even then they will still terrorize the others, Kenyi and Zebras are pretty nasty as well and should be kept with at least 7 to 10 others of the same species so that no lone fish is subjected to aggressive beat downs.. Even though a fight will still happen from time to time..

If you plan to keep these guys i would start right now on trying to buy a 75gal setup if money is an issue go to craigslist.com and maybe you can find a deal on a used setup, once you have a nice size tank for Mbuna you will need to beef up the species like adding 6 to 7 of each species that you listed except the Bumblebees leave their numbers alone because if you get a mated pair they will over take your setup and the other fish will be pushed / punked in the corner..

This information is not to deter you only meant to help and to be successful in keeping Mbuna..

Now if the 20gal is the only tank you can have at this moment and there is no possible way of upgrading to a larger tank then i would scrub the whole mission with Mbuna and go a different route like smaller Tanganyika shell dwellers.. Not as pretty as Mbuna but are African Cichlids none the less..

you asked if you are going to run into horrible problems later, the answer: most definitely YES!!! You have two species noted for their aggresion. While I'm sure it is a colorful tank at the moment I very much agree with the replies you have received so far. Your fish may live for awhile, but won't thrive, nor will you be able to observe the normal behaviors that Mbuna are known for. I'm guessing that you purchased these fish from a large pet store?? unfortunately they are common species for the large chain type stores but their true care and characteristics aren't supplied. Shelllies would be a neat use of the tank. Best of luck to you, a great source of fish would be a local fish club if one is in your area.

Definitely, a 20gal tank is not for mbuna; not for even the less aggressive mbuna species. As minimum, I would use a 3ft long tank (30gal) for a one species only dwarf mbuna setup; preferably of Pseudotropheus saulosi or Cynotilapia afra.

Now a 90gal would be awesome and will open the door to a nice African Mbuna setup I hope you get it my friend..