How long to leave the light on?

Greetings,
I have a biocube hqi, the one with the metal halide light. I have 2 little clowns, 2 peppermint shrimp, and an assortment of crabs and snails. I was running the light for 8 hours a day. The cleanup crew could not handle all the algae that grew. I noticed that there was barely any algae growing on the parts of the rocks that were shaded so I cut the light to less than 4 hours a day. The amout of algae has been reduced dramatically.

How long does the light have to be on? I would like to continue discouraging the algae growth, but I want to make sure I have the light on long enough to make everyone happy.

Thanks for the advice.

Algae is photosynthetic so having your lights on will increase its growth, however having a good CUC, good water parameters and the correct lighting really reduces it. I leave my lights on 9 hours a day and dont have a problem with algae. I would think that you probably dont have enough snails in there to be honest. Crabs are really great for getting leftover food and being creepy in general, but I would say you need more snails in there. They keep mine in check perfectly. What type of algae did you have in there?

Im not exactly sure what kind it is. I've posted pics here algae problem?

I thought crabs, only because I alwayse see them tearing away at the stuff. I've got lots of snail! I have about 25 dwarf creiths, 2 regular ceriths, 5 nerite, and 9 nassarius. The snails do a fantastic job cleaning the glass, but I hardly ever see any of them on the rocks.

ReefCleaners.org | Clean Up Crews and Macro Algae - Quick Crew (25 Gallon)

That is based on a 25 gallon tank, so you would need something bigger however honestly I just think you need a good CUC in there. The crabs are nice, but youll notice they are absent from a standard CUC, I never had a single crab in my tank, everything has always been taken care of by the sanils.

The crabs are jerks, they fight with each other and have killed multiple snails. I'm going to have to get rid of some if more snails are the way to go.

But, the light. Is there a good rule of thumb? How long should the light stay on?

Your lights should be on no more then 12 hours a day, most people stick around 8 though, I have my lights on for 9.

Crabs are sort of notorious for killing snails. I dont like to keep them in my tank because they kill my CUC and well.

THEY ARE CREEPY AND CLIMB OUT OF THE TANK

seriously though I think youll be far better off by beefing up the number of snails you have. I think the rule on nassarious snails is 1 per gallon and they will turn your sand over. You can keep a few of them if you really want, but my shrimps clean up what my snails miss.

My wife would lose it if she found a crab out of the tank.

Thanks for the advice.

You can thank my husband for my irrational fear of crabs. We used to have a tank with a few crabs in it. Well one crawled out and my husband saw it and put it back in. Well I totally freaked when I heard about it and he thought that was funny so he used to tell me that they were going to crawl onto my pillow while I was sleeping.....

I never ever heard of a hermit crab climbing out of a tank, you dont need to worry about that.


Also what are you feeding your clowns, how often, how often are you doing water changes, are you using tap water? All of these can effect your water quality and algae issues.