v1point0

What are your parameters? Algae problems tend to be a sign of high nutrient levels (Nitrates and Phosphates). Are you using an RODI system for top off and mixing your new salt water?

The algae in the tank is proof of phosphates/nitrates. Regardless of what a test kit says, that's something you have to accept and fix. Without those nutrients the algae wouldn't grow, and because of the algae growing it is using those nutrients so they're not left over to be read by a test. Get me? Got me? Good? (I was confused for awhile too lol)

So should I go for some Phosguard to help with he Phosphates? My refugium must not be doing the job well enough either then. I was using RODI but haven't had the time to mix so I have been getting my water from The Saltwater Wharehouse here in Dayton. I usually use RO water for top off. Should I just use RODI for all to include top-off? I thought RO was good enough for top off.

You want RODI for everything. Most likely their water isn't filtered well, and while those bits are ok for many fish only tanks, in reef tanks they play hell. Even after the RO process my water still has like 9 or 10 TDS, which means there is still solids in the water supply adding to the nutrient load. Your refugium can generally take care of tank demands, but when you're adding additional load by the top off water and salt mix, it just can't keep up.

The other thing to watch for too on an older tank is nutrients absorbed into the liverock. This wreaked havoc on me for awhile after I had seriously lacked on my tank maintenance.

I would definitely test your fresh saltwater and top off water. Test it for ammonia/nitrite/nitrate/phosphate on both. That way you can see if it's coming in by way of the salt mix or if it is present in the water before mixing.

looks like the tang has a Bacterial infection which usually stems from poor water conditions(build up sometimes called old tank syndrome or from tap water). You need to move to a Q tank and treat with some antibiotic. The water your getting from your lfs may be not what it is suppose to be. try blasting off the rock and do a big water change. Inverts always the first to go from bad water they are like canary's

something im considering doing to clean up my sand bed is 3 days with no lights combined with daily waterchanges to bring down po4, no2 and no3. you may want to consider this however your case im not sure how this would work...but its worth a try!

Ok, here's the latest. I just got done accomplishing a 24 gal water change (75g tank plus refugium). I made my own RO/DI (I've got Melevs RO/DI equipment) and used Instant Ocean Reef Crystals. Now you may ask, "well why didn't you away just use that?", and my answer would be that I have been too busy and just didn't have the time; so I made the time tonight. I have always tried to keep my salinity at about 1.026 so that's what I made the water to. I blasted all my rocks, cleaned out a lot of the crap algea in the tank and other algea in my refugium and now I wait to see if that will put me on my way to a better tank.

I did try the no lights method awhile back but it didn't help me in this situation. But if this water change doens't at least help, I'll have to do a combo deal with the no lights and water change. In any case I think I should do another water change in about two weeks of the same amount to assist my recovery.

I'll test the tank salinity tomorrow and make sure that it's where I want it and not over.

Thoughts?

It looks like you’re on your way; the addition of the DI should keep your TDS right at 0 for awhile which is definitely a good thing. I’m not sure if you have a TDS meter but I’m curious to know what your readings are: before, after RO and after DI just so we know how much of a difference this DI is making. None the less it was a wise investment but it may not be the culprit. I personally I’m using DI at the moment although I should (very bit counts) and I get between 1 and 2 TDS coming out of my membrane

IMO The 3 days of dark is really only to impede algae growth enough to let you catch up on water changes and get water quality where it should be

What I’m finally beginning to figure out is...if there is algae in your tank it MUST have a “food” source even if levels are undetectable. This means somehow there are excess nutrients in the water. Through process of elimination you must look at import and export and figure out where the problem lies.

Imports are going to be everything going in to your tank: top-off water, food , salt, even your hands
Exports can be anything from metabolization of bacteria, skimming to water changes

The list of possibilities is long in both cases but I’m sure after scrutiny and trial and error you can narrow down your source of the algae problem

***P.S watch out for TDS creep it will wipe out that DI resin real quick, its amazing how much longer it will last if you bypass the first minute or two of water each time you start up your filter