How to Avoid Greening?

[Biff0rz]

"How old is the tank?" is a somewhat more complicated question than you would think on the face of it.

The most literal answer is 5 months. That's not really the correct answer, though, because that's literally just how old the tank itself is. The system - the rocks, sump, etc - has been running since at least 2020. And a good chunk of the filtration in the tank - the rocks, especially - have been under continual use since 2016.

I've been dosing NO3 for about 6 weeks now, started shortly before I took that ICP sample, and it's now up to 12 ppm or so. PO4 is still about where it was at the ICP sample. I need to switch from lanthanum to something more long-term... I used the lanthanum to try and flush out all the excess phosphates on my rocks from 10 years of abuse, and I think it worked. After staying stubbornly high for a long time, I now see actual weekly fluctuation in phos numbers. Based on that, it looks like my system is producing about 0.2 ppm of phosphate per week.

As for the aluminum - I do have ceramic MarinePure spheres in the sump. They've been there since 2016, and I have had Al levels similar . Unless there's aluminum in the foods I feed, that would be about the only source for it that I can think of. That level has been pretty consistent for the entire lifetime of the tank, though I haven't done a ton of ICP testing. Going back to 2016, Al has always been somewhere between 20 ppb and 50 ppb.

So I get the whole new tank, old sump/rock thing - there is an adjustment period when you do switch over even when preserving a lot of it like you did. That could cause it, honestly.

If it were my system, I'd keep trying to be consistent with dosing and trying to balance the no3 and po4 as natural as possible.

I dont like metals in my tank and some systems adapt well to them. 30 seems a bit high for me on the Al. I'd replace those bioballs (slowly, lol) with some more live rock or new filter media. They do tend to leach Al.