How often can I do a water change

[sansouci01]

I've been having an algae problem lately in my 20 gallon tank. It's powdery green stuff on the rocks. I do a 3 day lights out and it disappears for about a week then returns. I practically starve my fish so not an over feeding problem. I do a 5 gallon a week water change. Should I do a larger water change after a 3 days lights out period and maybe a couple of more during the week or is that too much. My fish and corals are all healthy looking. It's just that the tank is starting to look pretty bad.. I'm running 4 t5's that are brand new. They are on about 8 hours a day. Blue plus and purple plus bulbs

[mr_X]

You can do as many water changes as you want. How is your source water and how about the salt mix?
....maybe it could be the source of the trouble.

[sansouci01]

I have an ro/di system. Water tests 0 tds. I use IO salt mix. never had any problem with it before so I am only assuming it's ok...

[mr_X]

Try a different salt and see if that cures the problem. I have always found IO products (regular and reef crystals, along with a few other brands) to leave a nasty residue in my 55 gallon mixing drum.

[JMorris271]

Do you use a fuge with some macro algae .I am think of phosphates here like LR leaching . A good CUC would be very useful too.
Instead of doing water changes forever, find out the cause and fix it. JMTC

[mr_X]

Originally Posted by JMorris271

Do you use a fuge with some macro algae .I am think of phosphates here like LR leaching . A good CUC would be very useful too.
Instead of doing water changes forever, find out the cause and fix it. JMTC

Wouldn't crabs, snails and starfish (a CUC) be ignoring the cause as well? I doubt adding more eating, pooping, critters is going to help lower nutrient levels, which I think we both agree is the underlying issue here.