Hi,

1) 340 gallon tank is a huge tank. You can hv a very nice setup. If me, I will get around 50-70 Haps in there. (there are different type of haps. They look fierce and more colors) If with correct biotope, some of them will grow to 8-10inch long. But sometime they will fight with each other till die. This is very common for cichlid.

2) Setup of a tank is depends or follow the feeling or view of the owner. You can just use whatever you have and setup. But the correct biotope shd hv sand bed. I was having the malawi setup with sand bed and rocks. And I never wash the sand bed or rocks. Why need to wash the sand bed or rocks? Since the bacteria growing and better not to disturb.

3) I kept my Malawi PH level at least 7.8... highest is 9.

4) The CA and SA cichlids are much more easier to keep. But they are huge than malawi. (just my 2 cents) Malawi sometime are quite sensitive with PH and temperature. And cant over feed them.

Space of the tank is a very important issue for any cichlids.