1.020 Salinity

[tdubrow]

Like an idiot I never calibrated my refractometer when I got it. Just did it today and realized my salinity is at 1.020. The fish and cuc are doing fine, so it seems. Could this be a reason why there seems to be a loss of coraline algae in my tank and not much life on the live rock? I was thinking of trying to get the salinity back up to 1.026 gradually by adding saltwater to top my system off instead of just ro water. Would this be ok?

Any other suggestions would be greatly appreciated. I'm such an idiot

[th08tu]

I'm not sure on your questions, but there is an LFS by me that has a specific gravity of 1.018! So I am not surprised your fish are doing fine.

The only thing I could see with the top off thing is that rate at which you change it. How much of your tank usually gets replaced each day? Maybe you could put in instead of RO water like 1.01 water and then it will slowly go up?

[tdubrow]

Originally Posted by th08tu

I'm not sure on your questions, but there is an LFS by me that has a specific gravity of 1.018! So I am not surprised your fish are doing fine.

The only thing I could see with the top off thing is that rate at which you change it. How much of your tank usually gets replaced each day? Maybe you could put in instead of RO water like 1.01 water and then it will slowly go up?

I replace 1 gallon every other day.

[Kurt_Nelson]

I would say topping off with saltwater is OK. That's what I've done when I've needed to bump my salinity up.

How big of a tank are we talking about? 75g or so?

[tdubrow]

Yup, its 75 gallons.

[cmor1701d]

So your topoff is 1 gallon per day?
Great, mix that up to 1.030 SG and use that for your top off till the tank slowly comes back up to 1.025.

Fish do quite well at 1.020, corals need it higher (as you found out).

How did you calibrate your refractometer? Did you use a solution or DI water?

I generally do both and check it quarterly.

[austinsdad]

Distilled water would calibrate.

[tdubrow]

Originally Posted by austinsdad

Distilled water would calibrate.

I used my RO water to calibrate. Is that ok or should I get some distilled water?

[austinsdad]

I dunno. CMOR??? You said it. Does it work?

tdubrow - I'd get some anyway. You can use the rest in the iron. Keeps the hard water stains at bay.

[CaptainAhab]

same thing.. pure water (assuming 0 tds RO)

[ccCapt]

RO/DI water will calibrate it for use with saltwater (saline solution), except we use seawater. To accurately calibrate it at 35 ppt (1.026) you need to use a calibration fluid.
If you calibrated with RO water, you will read a little higher than it actually is. If you see 35 ppt, it's more like 33-34 ppt.

Very good article on calibration here.
Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

[tdubrow]

Great Article. Thanks so much.

[cmor1701d]

There is BIG difference between RO water and RODI water. If you are using RODI water that is at 0 tds then there is no difference between using that and distilled water for calibration. But that's calibration at 0. To be sure you should always test using some standard calibration fluid (about $5) or make your own per the instruction in the linked article.