having some frustrating issues, help please

[lunker101]

I have a 50g reef that has been running for 2 years. Last year, i plumbed it to a 50g sump for water quality purposes. That sump has turned into somewhat of a refugium as there is tons of macro algae growing now (although it is barebottom). The main tank has about 310W of power compact lighting on it, the 50g sump/fuge has 96W. I also run a 24" CPR HOB refugium with crushed coral and tons of macro growing. 0 nitrates, 8.2 PH, 1.025 SG .0/trace phospates varrying between tests Up until a few months ago, everything was doing great. Tons of coral growth, no algae issues. Then last month i had a torch coral start to bleach out on me, along with an oxypora. I also started to get some red slime growth. I cut back on my lighting some (reduced from 12 hours to 9.5, however the sump/fuge light is on 24 hours) and increased my water change frequency. The bleaching didnt get any worse but the health of the coral certainly hasnt improved much, and the red slime is still in the system (i siphon it out but it simply comes back). Any possible ideas on how to help the coral recover/ why it happened in the first place and how to get rid of the red slime? I bought some red slime remover but i dont want to start dosing chemicals just yet. Should i stop running the sump/fuge light 24/7? Its very frustrating to have a tank run seemingly fine for 2 years and have everything test okay and start losing two of my largest corals for no obvious (to ne) reason. Please help. Thank you

[Sk8r]

Alkalinity/ph? Ammonia? Could something have gotten out of parameters when the new section came online?

[Avi]

You haven't said whether you've put new bulbs on the reef since you started two years ago and if you haven't, that's the first thing I'd suspect as the cause of those kinds of problems. If you have changed the bulbs and have been keeping them updated, then I'm suspecting some overfeeding but that's a guess.

[rdmpe]

Phosphates tested? Where does your water come from?

[lunker101]

bulbs were swapped out about 9 months ago. Phospates are 0. Any ideas? Should i change the lighting on the sump to just a 12 hour cycle instead of 24 hours ? I should state that the amount of red slime is low. Its on the occasional wall and rock but its not really growing crazy. Like I said, the corals dont seem any worse but certainly arent looking much better. Is there anything i can do to help the healing proccess?

[jdieck]

You have tons of macro in the sump and fuge. That might slow down the flow a bunch and accumulate detritus.

What kind of macro do you have and do you have a deep sand bed in your main?
What are your Nitrates?
What salt are you using and since when?

[lunker101]

the macro is half chaeto half caulerpa, i have been slowly taking caulerpa out and replacing with chaeto over the past year. Nitrates are 0 and yes i have a DSB in the main. I use Oceanic salt.

[Avi]

At nine months, you'd see here in RC that a lot of people recommend changing power compact bulbs. They'd look all right, but they lose their PAR over time and this could be part of the problem, both regarding the coral and the red slime, which is probably cyanobacteria. I suspect that it's bulb-related because the bleaching and effect on coral and the appearance of red slime in your tank are contemporaneous.

I'd change the bulbs just to be certain, since you'd have to replace them within a few months in any event.

Make sure you have sufficient waterflow in the tank. That, together with the new bulbs and regular and more than usual water-changes would address the damaged coral. It may well work over some time.

[jdieck]

On top of replacing the bulbs I will recomend a good harvesting of sump and refugium algae so circulation improves around it.
If the slime on the sand surface of DSB may indicate sand started getting full of detritus.