[jonwright]

I have an established 50 gal with "dry" rock (sat in bin for maybe a year, not pristine conditions!) that has cyano/dino taking over. Can't grow SPS or corals to despite never seeing nitrates or PO4 at detectable levels. Ceasing water changes seems to have helped greatly and allowing tank to get "dirty"

I also have a 155 that recently started with TBS rock in early November. I DO have nitrates and PO4 already in that system. I'd say it has maybe 40% dry rock (that is the same as the 50 gal above) and 60% TBS rock with no dinos.

What's curious: I took a couple of TBS rocks and put in my 50 gal. No cyano/dinos on those rocks at all. I've also seen cyano resurgence just a bit on the other rocks with NONE on the TBS rock. They have been present since @11/20 with zip, zero ugly stuff on them. None.

I've never been able to detect neither nitrate nor PO4 in my 50 gal. I also have 0 corals that utilize dkh, only a small clam, zoas, and an anemone yet to keep dkh at @8 I have to fully saturate kalk with vinegar in the ATO (using @1 gal/day).

I've been tempted to change water from my 155 to "dose" nitrates in my 50 gal and/or take skimmate and drop into 50 gal. Other option I think would be to initiate carbon dosing regimen (I've started that on the 155 already).

My current theory is that the bacterial balance in the 50 is all hosed up. I'd say it's had a dino/cyano problem for @9 months or so. Frequent water changes only made it worse (I did that for 2-3 months in hopes of being patient and persistent). What's helped the most is letting it run dirty for maybe @4-6 weeks (no water changes). I've added pods and dosing phyto regularly to hopefully change the tank, but after 3 weeks it's gotten better, but certainly not where it should be.

Where I'd like some help from the community here would be a positive ID on the critters present in my 50 gal (uscopes aren't easily had around here). I'd be happy to conduct one of the three options and share results with you all in a controlled procedure.