Corals bleaching/changing to natural seawater

[rapdiver]

I have a 75 gallon reef tank.I've been using Instant Ocean with Demin water. I've had problems with my corals bleaching. They all seem to slowly lose color and eventually die. Stony corals,leathers,mushrooms,star polylps, everything. I had same problem with a 155 gallon reef tank I had before.I had 155 reef tank for 3 years and everything was great then my corals started slowly bleaching.I had my water tested at several different fish stores and Roger Williams College. My water was within normal parameters. No NH3, Nitrates,Nitrites, Alkalinity was 9 DK,Calcium was a little low 380 .I had ample LR and had a deep sand bed in first tank. I increased byCa by dosing with Kent.Eventually I got disgusted and downsized to 75 gallon tank. The new tank with thin sand bed has been running for a year and same thing is happening.I've tested my tank water .Everything is within normal parameters. In both tanks the fish,shrimp, and carpet anemone are thriving.I was using MH lights on 155 and am now using compacts. I change lights about 10 months.I checked tank for possible contamination,found none. The only thing I can think of is maybe the demin water is too pure.The silica is .003 and conductivity is .6 umhos. Any ideas would be appreciated.
I have started using natural sea water instead of mixing salt.I know the quality of the sea water is excellent.I'm getting it from Roger Williams College in Bristol R.I. The water is taken from bay, skimmed, bleached, and then run through carbon.I wait 3-4 days before I use it.The water is used for aquaculture research at the school. Has anyone else been successful using natural seawater for their reef tanks?

 

[afsportsguy000]

My only guess and I am new to this is your lighting.

 

[JohnK]

Too pure make up water is not likely to be a problem. There are endless other things that can go wrong in a reef tank though.

Can you describe your husbandry routine a bit? You said you corrected the Ca level, but was that once or an ongoing dosing routine? What do you use to maintain alk and Mg? How do you replace evaporation? How do you measure SG? How stable is your temp (daily and seasonally)? What do you do for nutrient removal/managment? How and how much do you feed the tank?

 

[rapdiver]

I replace evaporation with demin water at same temp. of tank . I use a refractometr to check SG.I was using Kent 2 part dosing system on 155 tank.I stopped doing that with 75 gallon tank.Ca. is always a little low on 75 g tank but, I have an abundance of coraline alge on glass and LR.
I have a hang on skimmer . I had a skimmer in sump on 155 g tank.Temp. is stable at 83f. I add small doses of baking soda to raise alk. Feed tank dry food sparingly and feed anemone little bit of squid couple of times a week.I've been reefing for over 12 years and didn't start having problem until 2 years ago. The salt mix is replacing the Ca in tank.I have very light coral load

 

[JohnK]

"The salt mix is replacing the Ca in tank.I have very light coral load" With instant ocean? IO is normally a bit low in Ca, not high.

How often do you add top off and dose for Ca/alk? Stability is often the overlooked variable. Also 83 is on the high side for the temp, that could at least contribute to coral stress/bleaching.

 

[snowmaker]

I would agree with high temp. If my display hit 83'F I would expect to start seeing problems. I like a stable 78'F myself.

 

[Owen386]

I would agree with high temp. If my display hit 83'F I would expect to start seeing problems. I like a stable 78'F myself.

Put the Ac in today to keep 78 degrees LOL

To OP I`m curious to see your results after using NSW opposed to making it yourself. One guess to the problem your having is the variable of making up your water, what are using to mix in? Thinking there might be some source of contaminant in your mixing habits? Your saying no Corals survive in this tank?

 

[gweston]

I keep temp around 77-78, and use a salt mix with higher ca/mg/alk like reef crystals. I used regular IO and switched to RC with my newer system. Mainly to cut down on two part dosing. IO always came out a tad low on Ca and Mg. Not bad at all mind you. Just a tad lower than what one would call optimum. Water changes weren't bringing the levels up enough alone. Dosing 2-part helped. Kalk helped. Switching out reduced that need. I gradually shifted salts. I went to a 50/50 IO/RC mix for a month until I ran out of IO. The cut-over to RC went unnoticed by the tanks critters as far as I can tell.

But... can't say I have had major luck with all corals myself either. Palys, kenya trees, and softies in general seem to do rather well for me. The Pink birdsnest is currently borderline. The zoas all melted. My anemones, however are flourishing. That is with the 29g tank though. The new system is just barely out of cycle. I'm sure that will have it's own new and unique challenges.