A Penguin 330 filter is recommended for tanks up to 55 gal so you’ll be safe, though on the outer limits of its capacity. Some extra filtration wouldn’t be a bad idea with mbuna’s.
An Eheim 2215 could be an option as extra mechanical filtration but if I were you, I would go with a second Penguin 330. They’re good value for money, more capacity, perhaps even better filtration with the bio-wheel and easier to maintain without the hoses and stuff.
As for the substrate; sand would be the best choice when it comes to duplicating their natural environment. But also fine gravel(next to sand) would be a good replacement.
Some hobbyists use crushed coral (or a mix) to raise or buffer the waters pH/KH, whether you need crushed coral as well, will depend on your tap-water conditions.
Although I’ve never heard or witnessed any fatal accidents, course gravel could damage their gills as some mbuna like to sift sand through their gills in search for some food.
I hope you’re not too confused by all this, but if your goal is to create a natural habitat (as close as possible) I would definitely go with the sand.
Lots of rocks creating lots of hiding places are highly recommended.
Make sure not to place the rocks directly on the glass or on top of the substrate, place them on a piece of polystyrene foam like a half inch thick first, than pile up the rocks and after that you can add the substrate you’ve chosen. This will prevent the bottom from cracking (small pressure points with lots of weight) and the rocks from collapsing when your mbuna’s starts to dig, because that’s what they like to do.
Jimmy
