[Delphinus]

Sorry to hear J.

Personally I don't think this sort of thing really can be attribute to a deterministic number of parameters. In a sense, tanks just get old. It's not really something that we can say "oh ya, three years, old tank syndrome." But it is things like accumulations, and something pathogenic in nature that gains a toehold and that's really it until something gives (or you give, and either do a tank tear down or tank reset). Before anyone says "but he has UV and it didn't help", the problem is that a UV cannot get every single thing present in the tank. A couple months ago when Jason was looking for a UV, I even said it back then, I think it improved my own situation *some*, but: 1) it took close to six months to make a difference and 2) I still would not say I have a 100% turnaround. Some things are doing better, some things remain the same. I can't keep SPS anymore, plain and simple, it's a fact of life I've had to accept with some measure of difficulty and humility.

But, for what it's worth, I look at many new tanks with a measure of envy for what I see in them. I remember fondly the days of keeping colourful SPS, but it was years and years ago now. I truly do believe that newer tanks have an easier go of things, and older setups, due to many different and possibly uncountably complex interactions, a tank gets to a point it is not able to sustain growth that it used to, and it's not a case of something you can necessarily measure, like a stray voltage or a bad parameter or two or a salt brand or batch.

Sorry, I guess this isn't really helpful. You have my sympathies and empathy Jason .. I wish you the best of luck.