i've got 2 x mp10s in my 93 cube and they're at 70%. All my SPS are happy.

I have had very similar RTNs over the past 2- months. I actually tied mine to dosing Coral Snow. :(

I had similar situation lately, but now it is getting better. My issue was UV module I have installed on my Illumina fixture and introduced BioPellets in system. after a month with BioPellets and once reduced UV level to 20% my Pocci reestablished colors and Acro is purple again. Additional I have started to automatic dose Alk and Calcium. Not sure what worked best for me but all together made a change. Good luck!

I don`t think you`re setting your powerheads up very well then. :razz: Certainly you can`t place powerheads so they shoot directly at corals. The MP10s are only 1500 gph full blast which isn`t enough to push across a 48 inch tank. If the MP10s were situated on the back glass pushing towards the front more velocity may be able to be made. SPS though need a lot of water movement throughout the tank and appreciate velocity.

My 90-gallon which is very similar dimensions to a 75-gallon has two Tunze 6105 (3400 gph) and a 6055 (1450 gph) and I can run all of them full blast with the narrow outputs on them and as long as I have the powerheads situated well my corals will keep their flesh on. :D My tank has about 92x turnover where the OP`s tank has about 80x turnover. Even though these numbers are quite similar, the larger pumps in my tank create higher velocity.

The Tunzes`new wide flow output option is really cool because you can get the same amount of flow with less velocity. LPS do not appreciate velocity. :lol: In a mixed reef like the OP`s, creating flow that makes all the corals happy is challenging.

Chizer, I would try moving those MP10s around to create more velocity near the SPS. If you set them up on the back glass pointing towards the front glass you should be able to achieve this. The VorTechs can be a bit awkward though since you can`t control their direction.

It could very well be the tap water though. :)

I wish that was an option. I have a large coast to coast external overflow on that entire back wall so it limits me to placing the MP10's at the bottom half of the tank. I had thought about building my rock up with PVC and laying them on egg crate, then it would give me that velocity.

What do you think? Will this look tacky? My SPS will then be about 6" from the surface.

I am going to buy a RODI unit from BRS. Just looking at the cost of RO in my city, it's going to be $40 just to do a 40 gallon water change. That's not including the ATO water of 15 gallons a week.

Also going to try some BRS GFO in a media bag, in my filter sock. But I'll put it on the output of my protein skimmer.

I really want to get a way from carbon dosing entirely. It's scaring me off. :redface:

I am thinking it was a combination of ALK ( initially at 7 and then I slowly raised it to 8), and bad water quality. Lesson learnt, listen to people's advice as they have been there, done that.

how can that be? I have been using coral snow for a year and never had any bad effect with it.

What made you beleive it was coral snow?

If you are paying for your water, then you might want to consider a RO unit that is low on water usage like this one, which will waste no water, so cost much less at the end:

http://www.costco.ca/Premier-Zro-Pur...100016456.html

If you are using tap water I would start with using RO. This is probably your problem.

Yeah, it probably will. If you don't have something laying around you could use (like a cheap Koralia that you can put the back magnet into the overflow) then just try the RO. Your SPS are fairly small still, so it may not be a flow issue. As they grow you're probably going to get some trouble. If you see a good deal on an MP40 I would probably pick it up if I were you and replace two of the MP10s with one MP40.

Ouch. Yeah, that's a good plan. Talk to someone in your area that knows RO/DI systems really well to figure out which filters types work best. Here in Saskatoon we have chloramines to worry about, in Alberta I know many areas have really high iron content. I have no idea how that may or may not affect RO/DI systems. If you don't know a fish RO/DI expert, ask a drinking water company and just tell them you're looking at options for drinking water. They will tell you what you need for stages, and then buy it at BRS for 1/4 the price. :lol:

I don't think it is the alkalinity. Tanks that run biopellets are prone to RTN if the alkalinity is above 8 dKH. Zeovit tanks are also supposed to run around 7 dKH. Natural seawater averages around 7 dKH. My reefs both run 7-8 dKH.

Thanks for the link Daniella. That was the main reason why I didn't purchase a RODI in the first place. It just wastes so much water. I'll check out that unit you posted.

If you are running zeovit to lower nutrients then definitely get your dkh down to 7-7.5 and keep it stable there. I started zeovit in my tank 2 months ago and I can say that higher dkh than that you will start noticing burnt tips on some acros which will lead to stn. That's just my experience so I would try to work on lowering your alkalinity.