lowest possible salinity for corals?

[astroboy]

Hello!

 

A couple hours ago my sump was making strange sounds. The water level was a good deal higher than it should have been. What I think happened was that the automatic top off got stuck, perhaps because I had it turned off for a few days which allowed the float to stick. I guess the moral of the story is to never turn something off and assume it will function properly when you turn it on again. Fortunately, the shut off switch worked fine.

 

Anyway, the salinity (specific gravity) has been at 1.021/28 ppt for a few hours. Corals and fish seem fine, despite what must have been a rather rapid change in salinity downward from 1.026/35. I suppose since the automatic top off sends water into the sump perhaps the change was a bit slower than it might have been.

 

I'm going to raise the salinity back up by adding salt water to replace evaporation losses over the next few days.

 

But it occurred to me, generally speaking, what is the lowest salinity corals will tolerate? I'd be interested in hearing first hand accounts. Most of what I found on the web was second hand or otherwise questionable....

[jimlin]

I think it depends on the type of corals.

when i first started sw, the guy i bought the tank from said salinity should be at 20ppt.

thats what i had it at for about two weeks until i done more research. at the time i only had pest corals and they were thriving.

brittle stars also made it.

[smallreef]

I have seen them in shipping water at 1.020

[Dr.eclipse]

are you talking long term? or just a mistake, short term?

[Jan]

I think I post this every 4 months or so.... http://www.reefkeeping.com/issues/2004-05/rhf/index.php

[jaddc]

Experiments show that coral can survive down to ~20ppt. Less than that and the actually coral will die and fall off the skeleton. Caveat-each coral is different...some are more tolerant other less so. However, the zooxanthellae are negatively effected at lower salinity and so reversible bleaching will occur. If you want more info "hypo-osmotic stress" is your keyword.

[treesprite]

I've over-diluted my tank at least 3 times dropping SG to as low as 1.15. Corals never had a problem, by all my snails died at 1.15 for several hours.