[Floyd R Turbo]

Originally Posted by SantaMonica

Sounds like what I was saying. Acros are mostly rock, and any transfer of rock through the air kills a part of it, and causes die-off. If the 4-cube scrubber was already thick, the extra phosphate might have made growth thick enough to kill the roots and let go. If so, it should be back to normal soon. Larger screens just have less water access from the edges of the screen, so the middle dies sooner when thick.

But that quote is not accurate, here is what he posted

Originally Posted by sensei

I did not have a pump failure.
something did happened in the chemistry of the system, since I introduced around 12 acropora frags 1 month ago and in the last 15 days I have noticed some burned tips, and it happened to be at the same time that I had this whitening effect, but I did not know until I cleaned the screen last week. I have not been able to know why the burned tips since kh has been stable and it only happened in the new acros, not on the established acroporas.
can this whitening effect of the algae release some toxins in the water?
phosphate increased from 0.02 to 0.07 but I guess is becuase the 4 cube ATS was not working.

So the "extra phosphate" would not likely have caused the scrubber growth to fail, otherwise the 2nd scrubber which is also on the same tank should have died off similarly. But that didn't happen.

Originally Posted by SantaMonica

No, dying algae just put nutrients back into the water.

I'm not so sure about this. While it seems to make sense from a logical perspective that whatever nutrients the algae has adsorbed in the process of growing would be released when the algae dies, it's not likely in the same form. Also there is probably something else released when algae dies off, like sugars.

But the rise in phosphates is probably a combination of the filtering being less prevalent + the nutrient release from the algae dying. However I think the nutrient release is less of a factor since this seems to have happened shortly after cleaning...did I get that last part right?

So the timeline is:

12/3/17 added acro frags
12/19/17 = Day 0 - cleaned scrubber, normal looking harvest
1/2/18 = Day 14 - Noticed scrubber is white

Now, another piece of info (posted 1/3):

Yesterday cleaned both after last hasvest 14 days ago and to my surprice the 4 cube did not show any growth and the little algae attached to the screen was completelly White, what could have happened??

What this tells me is that right after you cleaned the screen, something happened that caused whatever growth you have to stop growing and die off, and it stayed that way for the 14 day period. So this would mean likely very little nutrient release since there was very little algae.

Is the growth on the L2 just fine? Normal looking harvest?

If so, this just seems to point to an issue with the settings on the L4. A temporary pump failure would make the most sense. What you want to look for as evidence to indicate this is the presence of white encrustation on the screen, stuff that looks almost "baked on". If this happened for a few days right after you harvested, but then the water kicked back on, it would still be white and crusty/hard.

Tell me about your pump controls - do you run the scrubber pumps off of a controller? Or do you manually plug/unplug them? If on a controller, is it possible that you didn't re-start the pump after cleaning, but the controller kicked it back on automatically a day later as part of a fallback mode?

Tell me about the settings on the L4 and L2 - how many hours/day are the lights on? What intensity are they both at?