Salinity / Specific Gravity formula

[topofsteel]

I have a 55 gallon tank with specific gravity of 1.019 (there are no fish in it) and I want to raise it to say 1.022. If I were going to replace 5 gallons of water what specific gravity would that 5 gallons need to be to achieve this. Any chemistry professors out there? Thanks.

 

[susieq]

Since you don't have any fish yet, I think you're trying to do it the hard way. I would dissolve salt in a plastic cup, maybe 1/2 cup in 12 oz of ro water. Then add to the 55 until it has the right sg. Your trying to raise the sg by .3%.

 

[topofsteel]

Well there were fish in it, and there is still a couple of small hermit crabs and a very live rock. A larger hermit crap and 2 clowns died this week and I'm not sure why. My specific gravity was reading really high so I replaced 10 gallons of water with just RO water. It turned out there was a bubble in my hydrometer. I feel awful about it. All readings were 0 and the pH is 8.4. The fish stopped eating 2 days before i did the change and never started again. Plus one of them looked like it might have gotten pinched by the crab, if that's possible. If i increased my specific gravity to 1.023 or 1.024 will this kill anything in my live rock? By the way, 5 gallons at 1.026 increased the 55 gallon tank to about 1.021. Thanks.

 

[susieq]

Something doesn't sound right. That sg should be fine for everything in your tank. I have my 55 at 1.024 and everything is fine. It's usually sudden shifts that cause problems. I'm sorry about your fish and crab. Good Luck

 

[topofsteel]

Yea, the shift is what I'm worried about. If i jack my specific gravity from 1.019 to 1.24 today will this kill anything on my live rock?

 

[nano_nut]

since you still have some livestock I would leave the saline alone for now since you just raised it significantly. Maybe wait a few days and do the same process again except maybe change less water or use a lower saline water change so as not to change it so quickly again. a reading of 1.023 would prolly be better than 1.022 anyways. By the way if you can afford the upgrade (assumeing you can since it's a 55g) purchase a Refractometer as fast as you can so you can avoid these kinds of screw-ups. They seem expensive at first but once you consider the cost of livestock you've lost...well it pays for itself quickly.

 

[susieq]

I agree.