Is a low S.G. Killing my acro's?

[MCCOOL]

Hello all,

over the course of the last couple of weeks, about 60% of my Acroporas have started rotting from the tips down. They haven't completely died yet, but are clearly in distress. I've tested everything I can think of but had yet to come up with a conclusive problem. I've got a 60 gallon tank with a 20 gallon sump, a swc200 skimmer and a 6 bulb ati sunpower t5 fixture.

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Parameters are,

ph 8.4
nitrates <10
kh 9dkh
calcium ~480ppm
mag 1400ppm
phosphates are undetectable on my test but I don't have access to a Hanna meter, Although I do dose 2ml of vodka daily and don't have any noticable algae growth.

Now to the problem,

I've been testing my specific gravity with my refractometer and it's read 1.026, but my hydrometer has been reading 1.022. I was reluctant to trust the hydrometer, so I ignored it. Well I just tested my s.g. Using a pinpoint meter and it also read 1.022. Could this be the reason my acro's are dying?

On a side note, please don't use RO water to calibrate your refractometer!

Thanks for any help yall can offer.

 

[scrapz]

how long have you been dosing vodka?

vodka users tend to notice alk burn with alk at 9+

 

[MCCOOL]

I've been dosing the vodka for about a year now, although I did just bump the alk up to 9, from about 7. I initially thought it was alk burn before I tested, but after testing, I assumed an alk of 9 wouldn't do it. I'll try bringing it back down to 8 and see if that helps.

Thanks for the help

 

[scrapz]

no problem, good luck.

 

[buy_baff]

It's the Alk bring it back down a bit.

 

[sedor]

Could be the Alk, but I run mine at 13 and I also dose about 20ml of vodka into my tank daily. My guess would be instability. If your SG and Alk and likely Ca are constantly jumping around your going to have problems. Keep things stable and make slow adjustments and you won't have nearly as many issues.

 

[MCCOOL]

Buy baff- thanks, I'll try lowering the kh to 8.

Sedor - thanks for the advice, my salinity, kh and calcium don't really fluctuate at all. I intentionally raised the alk from 7 to 9 recently, but aside from that it only goes from 8-9 daily. The salinity doesn't change at all.

 

[Paco]

You need to raise your salinity and buy a bottle of calibration fluid

 

[InsaneClownFish]

IMHO 1.022 is low for an SPS tank. I keep my SG 1.025-1.0265 in all my tanks.

 

[jackinfobo]

Agree, raise your SG, but I honestly don't see a problem with having a high ALK. I ran my system for several months with an Alk of above 13Dkh and had no problems

 

[buy_baff]

Could be the Alk, but I run mine at 13 and I also dose about 20ml of vodka into my tank daily. My guess would be instability. If your SG and Alk and likely Ca are constantly jumping around your going to have problems. Keep things stable and make slow adjustments and you won't have nearly as many issues.

This ^ is very true. When I first got into sps I had a lot of alk swings and my acros all started to get these weird nuckels on the tips. Got things under control and things straightened right out.