I have Malawi cichlids.I like to have my lights on in the aquarium and watch my fish when I get home from work. However, I am constantly cleaning the algee off the glass and rocks to keep it clear. Assuming that I am correct in saying light will causse algee to grow, can I keep the lights off in the aquarium during the day and just turn them on at night for 5-6 hours? Do they need a certain amount of light?