Too much light?

[daniejd]

I have a evo 13.5 marine, just using the stock light. It’s roughly 100 par at the bottom, but more of a daylight/yellow than blue. My corals in that tank are soft rugged types. GSP, Xenia, Disco, yellow polyps,  Rhodactus, waving hands, palys, gorgania. I like the light but could it be too strong? Take my palys for example. They multiplied quickly, but lately the polyps have started shrinking and fading. Same with Rhodactus. Yellow polyps are affected at all, Xenia and gsp have stopped spreading (though that may be the yellow polyps keeping them in check). I don’t think it’s the water, I’m pretty diligent in monitoring the numbers and change about 10% at least every other day. Also I notice they look better (color up) when the lights are in the sunset phase. I run a 12 on 12 off cycle.

[Wonderboy]

This could have something to do with the photoperiod - try reduce your on time to 8 - 10 hours and check the response of things - may have to do with the increasing biomass producing more oxygen towards the end of a day shift therefore depleting iodine - with that many soft corals, I wouldn't be surprised despite the systematic WCs.

 

It could be accumulated alkalinity - many salt mixes have higher alk to replace what has been used; if your corals aren't using it up, adding more every couple of days may add up.

[seabass]

Water changes won't increase alkalinity past the level that the salt mixes to.  However, despite your not thinking it's the water, I am wondering exactly what the parameters are, and which kits are being used.  It could be due to lack of nutrients.

 

Knowing how old is the system, and posting some pictures might help us help you.  Is there any coralline?  What about cyano or other issues?   Any leather corals which could be waging chemical warfare?

 

The intensity of the light doesn't really concern me.  Is it an LED fixture?  What about dosing, filter media, and water source?  It could be one or several contributing things.

[daniejd]

Ammonia 0-25, Nitrite 0-25, Nitrate 10 (Last night was my weekly deep cleaning always spike the day after, normally run closer to 0 across the board), Stocking level is heavy (4 fish, 3 crabs, 5 snails). Fish/crabs fed once a day, coral fed once a week. Test kit is api, no phosphate test kit. Crabs growing a lot (Mexican blue crabs, each has molted 3x in as many months). Some cyano in back, but kept under control and has stopped spreading. Tank is new (6 months), so coral hasn’t spread to cover all rockwork. Some green algae on bare rock. chemical warfare would be the yellow polyps, they are growing the best (from approx 4 polyps to 30) and fry any Xenia or gsp that gets near them, however the palys and Rhodactus are at least 8 inches from them. Sorry at work so can’t post pic.

[seabass]

It could be a lack of phosphate, which should be at least 0.05ppm.  Don't get API's phosphate test kit because it's a high range kit and can't detect the recommended minimum levels.  Salifert's kit is fine, but slightly hard to read.  Hanna's Phosphate Checker is more expensive, but it's often recommended to more easily determine these lower levels.