Firemouths grow large, don't they? I think 6 - 7" maybe? If so, they need at least 30 - 40 gallons of water. I think there is also one Firemouth that is a fake Firemouth Cichlid that grows to around 16" and needs a huge tank.
Bala sharks need at least 120 gallons of water too ... as they grow up to 14" in size (and they like to have a lot of space for comfortable swimming).
Besides, very nice photos Your fish are beautiful However, a 20 gallon tank is way too small for any Firemouths and Bala Sharks.