Full rock replacement planned

[mpderksen]

In previous threads, I've gotten a lot of advice about my lengthy GHA battle. I'm still not at all sure what kind of algae it really is. I've tried AlgaeFix Marine, black-outs and light adjustment, 2 sea hares, an abalone, turbo snails, tuxedo urchin, tangs, full H2O2 rinsing of every rock, and GFO. The previous owner used tap water for YEARS, and the only thing the Reef Central Borg mind can come up with is that there is PO4 embedded in the rocks, and still leeching out after over a year. PO4 remains at zero based on my HANNA. The other suggestion has been to ditch the GFO and build a turf scrubber. But I'm quite ready to be rid of these rocks anyway if they are a true source of the problem. Coraline is just starting to spread after a year, and the corals are growing, even my first SPS is encrusting, so other than the GHA, I'm very happy with the overall tank. But I pull large clumps of algae every week, and it continues to spread into my corals, covering and killing some of my nicest Zoa!
SO, I bought #55 of Reef Saver South Seas rock and have been cycling it in a separate tank for nearly a month. It should be ready in a few more weeks. I plan to swap ALL the existing rock with the new stuff, and add some Marine Pure 1 1/2" balls to the sump. New sand will be added slowly after a month or 2. I have a fairly light bio-load, and a Reef Octopus skimmer, so I do believe that #55 of rock in a 75 gallon is enough, even without a sandbed for a while.
I will move all the corals I care about to a separate tank, pull the rock and sandbed. Then add the new rock and watch it for about a week with fish only in the DT. Once I'm sure I don't have a cycle, the coral will go back in, but only the ones with no sign of the GHA.
The question is that since it takes only a single strand of GHA to recreate a full-blown reoccurrence, is it even possible or necessary to really sterilize the DT while I do this? Short of draining and bleaching EVERYTHING and using all new water, aren't I looking for all this effort going to waste?
If the true problem is that the old rock was feeding the GHA, I would assume that if a little is in there, the food source of PO4 will be gone and it won't grow back. Perhaps I should dose AlgaeFix Marine and do a 3-day blackout the day I put the new rock in as well? Since it will be fish-only for that time period, I'm pretty sure everything will survive. Some Nori on a veggie clip in the dark is probably sufficient for that amount of time.
Any other suggestions? I don't want to go through all this and come back a month later to where I started.

[thegrun]

In the end one way or another hair algae will be introduced into the new tank, so I wouldn't spend too much effort trying to prevent the inevitable. Focus instead on keeping the nutrients low and when hair algae is introduced into the system there will be nutrients for it to feed on and get established.

[jrp1588]

I'd 'cook' the rock for a while before I'd get rid of it. Soak in in RO/DI for a while with some lanthinum chloride replacing the water regularly. It's a slow process, but you know you'll have clean phosphate free rock in the end.

[mpderksen]

Originally Posted by jrp1588

I'd 'cook' the rock for a while before I'd get rid of it. Soak in in RO/DI for a while with some lanthinum chloride replacing the water regularly. It's a slow process, but you know you'll have clean phosphate free rock in the end.

Solid advice, thanks. I will eventually want it for another tank, almost certainly. No reason to dump it if it can be saved. Too bad I didn't think of this during the year I had it sitting dry in my garage for a year before I used it. Just never crossed my mind....

[mpderksen]

Two weeks update:
Slight amount of brown algae on the new rocks, but no sign of a cycle. The small bits of GHA that I didn't get out during the transfer have gone away. I think my Kole snacks on it.
I've seen a bit of a chain reaction, though. Since the GHA wasn't there, my PO4 is slightly elevated. Tonight it's up to 0.04, and was 0.02 on the 1st when I did the fresh 1/2 cup of GFO. Plus, my Ca and Alk has dropped to 380 and 8, respectively. I'm seeing growth in my SPS for the first time in a LONG time, so here's my theory: without the GHA, there is a small, but measurable about of PO4 in the water, so the SPS grows, and is sucking up the Ca. I've read that SPS actually like a little PO4 in the water, but since the GHA out competed it, it just didn't grow. Tonight I increased the dosing pumps from 3 min to 4, and I'll test again this weekend.
Previously, the 3 min was enough that my Ca and Alk were the same before and after the water change.

[whosurcaddie]

Read this OP he goes into full detail of how he cooked his rocks a few at a time. Even if your decide to replace the rocks its still a good read.http://reefkeeping.com/issues/2008-07/nftt/index.php

[mpderksen]

Thanks. I did replace all the rocks on November 1st. The update is the result.

[mpderksen]

So today is about 6 weeks since the full rock replacement for my 75. No signs of GHA in the DT other than 2 small clumps in the sandbed in back corners that don't get much flow.
(Sorry again to DLreef for posting the below in his/her thread).
Today, while doing regular, weekly maintenance, I pulled the cover off the back that is on top of the overflow to make certain the Herbie was at the right level. I found some GHA on the backside of the overflow teeth.
All together it was about the size of a golf ball. The cover is clear acrylic, and since it's mostly under the light, where the fish and CUC can't get to it, it's the perfect place to build up.
I know total eradication is impossible, but since I'm running GFO, rinse my food and have lowered the lights, it should be possible to stop the growth, right?
Should I paint the overflow black to stop it from growing in there? Or do I still have underlying problems I should address?

[mpderksen]

Picture is upside down...
ImageUploadedByTapatalkHD1418536056.287139.jpg
Dang it. Again. Just flip your monitor. Lol