By Request - green tank pics

[Delphinus]

Well I do want to jump in and claim that it can't be the tap water, because I've used our tap water exclusively for 4 years, and I have yet to have a problem that was caused by the water supply (plenty other problems cause by plenty other things, including stupidity of the tank daddy, but let's not go there.)

But the bottom line is, I am convinced that the phyto is living off something. So we have to systematically eliminate the variables, and that does include the water. (For now. [img]tongue.gif[/img] )

A 100% water change seems drastic and expensive, but it's not really akin to shutting the system down. The sand, the rocks, etc. will still have topical baterial cultures. It won't be a "back to day one" for the biological filter.

(If it helps you decide, I'm considering a 100% water change on one of my systems [after it was implicitly suggested by Rob/Biogeek last week]. I need to buy some time on this one tank with a nitrate problem while I decide what to do with it, take it down, or run it in series with another tank that CAN reduce nitrates..)

But the flip side of the coin is, if the source of the problem isn't eliminated, water changes arguably are probably only going to dilute the problem and prolong the agony. It would be treating the symptoms, not the cause.

This may sound dumb, but have you considered running your old Iwasaki over your refugium? I bet you could get your caulerpa to go nuclear with that thing. It would probably take a few weeks though, for it to start to outcompete the phyto, since the balance is seriously tipped in the phyto's direction right now.

I dunno. I know I would be seriously dejected were it me in your position. Keep slogging at it: we'll figure this out.