No SPS growth... stumped

My SPS have completely halted growth in the last month or two. On top of that, PE is greatly reduced, and a few have started to brown out. I feel like I've tried everything, and am completely stumped. They were growing quite well before I started running biopellets, but since then, its been downhill.

New bulbs (ATI) about 2 months ago. Had biopellets running, but removed those last week and have started vodka dosing back up again, now running GFO again. I use RODI water. GAC in filter bag. Tried adjusting flow a few times.

Using API liquid kits, everything has been consistant in the last 6 months with the expection of PH dipping to around 8.0 for a few weeks. Currently do not dose anything except Reef Buffer in the ATO water for keeping PH around 8.3.

NO3 - undetectable
PO4 - undetectable
dKH - 9-10
Calc - 440
Mag - 1800 (high, salt mix is suspect, but shouldnt affect SPS like this)
PH - 8.3
temp - 80
SG - 1.026

I'm thinking as of right now, continue vodka dosing, GFO, GAC, and reef buffer, trying to keep everything as consistant as possible for a prolonged period of time. I know SPS dont like change, and I feel there's been alot of change going on in the tank as of late.

Any advice? What causes polyps to retract?

 

I would try to keep alk a little lower since you are carbon dosing and I don't know if I would worry so much about keeping Ph at 8.3. I know that's what more recommended but mine is at like 8 fairly steadily and everything is fine in my tank. Also with carbon dosing you should end up feeding the tank more to keep nutrients in the tank.

Sent from my DROIDX using Tapatalk

 

Have you checked for red bugs? Are you feeding your corals?

 

That's what I forgot to mention flatworms and redbugs. The flatworms are next to impossible to actually spot but you should be able to see bite marks faintly and look for brown eggs at base.

Sent from my DROIDX using Tapatalk

 

I have not noticed any red bugs on close inpection, but I can look again tonight. Feeding the fish daily, and they poop alot. I wouldn't think a nutrient deficiency would cause the corals to brown though?

I would try for lower alk, but the salt mix I have (IO) is mixing at 10 dKH, 450 calc, and 1800 mag @ 1.026. Pretty high for IO, maybe the batch was bad?

 

Red bugs are really really hard to see with the naked eye. Use a magnifying glass if you have one. I had no idea that I had them until I took a very close up picture of my coral with a macro lens. I would never have known they were there if I hadn't done that.

I don't believe that sps corals get enough nutrition with just fish poop so you may want to look into what micro foods are available these days even if it's not the cause of your problems (I've been out of the hobby for a few years so I can't really say what's out there these days).

 

I will check for pests tonight. The PE retraction is widespread, from montis to acro to milli.

 

What is your flow rate like??

 

Few thoughts. Switching bulbs can be stressful, so can cause some stunted growth for a while, especially if the old bulbs were getting weak, or there was a change in spectrum. Same with changes in water chemistry (things you can and can't test for), which is likely, due to some changes, such as vodka and GFO. Perhaps even there is a food source such as bacteria, which was living off the BP and crashed when you changed to vodka and GFO. Polyps extend in response to chemoreception, so, if they are retracted, this could certainly indicate insufficient food. Do they extend at night?

The mag seems high, I'm not sure that mg would cause stunted growth or not, but impurities that go along with mg could. So, depends how it got that high, if the test kit is correct anyways.

 

The browning, stunted growth, and lack of PE started occuring before the switch back to vodka. I actually think most of this started when I switched to BPs, which leads me to think you're probably onto something. I'm sure all the switching hasnt helped (Stability Promotes Success).

The most confusing thing to me is the browning (which typically indicates low light or high nutrients) along with the polyp retraction (which typically indicates low nutrients?). Seems contradictory.

Mag kit is correct, I've verified that. The salt mix is mixing rediculously high. I'm out of that salt, so hopefully mag comes back down eventually.

Flow is fine for SPS. These corals have been thriving for the last 8 months with the same flow, it's just the last 2 that somethings been out of whack.