Diatoms or Dino killing Chaeto??

[easperhe]

All,

I'm a rookie and have my 90 gallon tank running now for ~2 months. I did not light during the cycle and have had no algae of any kind. After the cycle, I replaced all water (RO/DI) to get rid of nutrients that built up during cycle. I added 2 clownfish a week ago. I just got LED light for display but haven't turned it on yet.

I started to light my fuge (both 5000K LED and then 6500K CFL) to try and get newly bought Chaeto to grow. I have pretty good nutrient values already. But, I figured I would try and lower NO3/PO4 some and I thought Chaeto would live on low nutrients:

NO3: 1.5 ppm
PO4: 0.12 ppm

Chaeto looked ok at first but now is dying off. Where the Chaeto was dying the most, there is brown stuff on the rocks. Seems like brown stuff is out competing the Chaeto. There are little air bubbles too. Is this diatoms or dino?

[dppitone]

Doing a 100% water change is pretty radical. The water is teaming with good bacteria after you cycle it so you removed it all. That's not a method I've ever heard of or experienced so I can only guess on what effect that would have. As far as your macros dying - that's a symptom of a problem they're having with the system. It's hard to say what it is without knowing more, but generally speaking I'd say just try again with them in another month after the system matures some more. Macros fill a need and you may not have that need yet with only two clowns in there.

[easperhe]

Doing a 100% water change is pretty radical. The water is teaming with good bacteria after you cycle it so you removed it all. That's not a method I've ever heard of or experienced so I can only guess on what effect that would have.

To be clear, I cured the rock for a month, did 100% water change, then cycled the tank for another 3-4 weeks. BRS recommended the 100% water change (so it can't be that unusual). And, I would definitely recommend this approach. After curing the rock, my NO3 was ~40ppm and PO4 was ~3pmm. After the water change and 3-4 more weeks, the NO3 was ~2ppm and PO4 was ~.2ppm. So, getting nutrients out was great. I did put the rock (with beneficial bacteria) in a tub full of water so the bacteria on the rock was preserved.

[thegrun]

Chaeto does best with good strong lighting and the chaeto up near the surface of the water, it's hard to tell from the pictures but yours looks to be submerged several inches underwater. Your also looks spread out thin, it also does best when kept in a fairly tight ball.

[easperhe]

FYI - the diatoms in the fuge have gone away for the most part. I got some snails to eat them. But, I think the diatoms burned through the silica and have thus died off. Most of the chaeto died off too. But, I do have small bits of chaeto within the rock that now seem to be growing. So, my guess is that the diatom bloom ate up all the nutrients thus starving the chaeto.

The other thing I did is add a very small powerhead to the refugium area. I realized that there was very little water flow in the lower portion of refugium. I've read where this could help with chaeto growth.

[dppitone]

Thanks for update. Sound like your system is beginning to age, looks good.