What is the good saltwater tank chemistry?

Question

I just tested my fish tank for the 1st time. The tank has been good for more than a year now and just recently I notced some orange algea that is spreading accross the gravel which comes back if I turn the gravel up. Its not over feeding. Here are the test results.
GH-120
KH-240
PH-7.5
No2-.5
No3-40

I pretty sure I read the test right. I just got a lawnmower blenny and a scooter blenny to see if they clear it up, but I havent seen any changes yet. All the fish and the anemone are doing great so I dont think anything is too wrong, it just seems like some kind of algea bloom because I saw some hair algea growing which is unusual in my tank.

I do a water change once a month. Usually 1/4 to 1/2 the tank. The weird thing is that it started a couple days after a water change. An emerald crab did die right as it began. The filtration is a millenium 2000 and I change the filter bags regulary

Answer 1

From the results you're showing your pH is low - for a saltwater tank with inverts, it should be in the rage of 8.2-8.4. This can be a problem if you're on municipal water, since they usually add water softeners which lower the buffering capacity. You may need to add kalkwasser to bring the pH up. It comes as a powder that you mix with water in a separatte container and add using a doser (drip bottle like an IV in a hospital) or in small amounts (using something like a medicine dropper) this stuff ic caustic, so be careful on handling it and adding too much at a time. Can't give you an idea of how much you'll need to bring it up, because that will depend on the tank size and alkalinity/acidity of the water (this is different than pH, which is a result of the interaction of these).

For a year old tank, your nitrites should be 0. the nitrates are also on the high side. I'd say part of this is from your water change routine. You should be doing weekly changes of 20-25% rather than monthly. It will help keep the nutrient levels down, since you can't reduce your lighting because of the anemone, and also replenish the calcium, magnesium, and other elements your organisms use up from the water. With less nitrate and higher pH, this may help your problem with nuisance algae.

You might also want to add a phosphate pad if you're on a public water supply. Water companies can add phosphates to prevent pipes from corroding, and phosphate is a plant fertilizer (as is nitrate), so algae will use them as well.

Answer 2

iirc, no2 is nitrite and is toxic above 0ppm. nitrates should be lower, shoot for 20ppm or less and for delicate inhabitants(like your anenome) then try to keep them under 10ppm. how often do you do a water change and how large? what is your filtration like? what other fish do you have? it could be coraline algae. lowering your nitrates will probably be enough to reduce the algae unless you've got a lot of phosphate that isn't being used up by something else(like some marine plants)