Dave - I`m sure they will mines only smallish maybe just over 2.5" I think he`ll look better when he grows a bit.
Ashbreed - Thanks I think I could get a few more in but I wouldn`t like to go over board maybe 20 in total ?
I use a Fluval 305 (1000lph) it seems to work fine for me and maintenance seems easy but I`ve never used anything else but you`ll find they don`t have a good reputation at all Fluval canister filters that is. I might need to upgrade mine anyway eventually as Mbuna require more filtration than normal upto 5 or 7 x your tanks capacity.
Eheim seem to get good comments from most people and do look well made.
Siam - Thanks.