[Nikki]

Hello ;-) I am starting a salt water tank, 46 gallons with the intention of providing my daughter with a Nemo for her birthday. Read a couple of books and am going to add some live rock as well. Have a Dual Bak Pak skimmer, eheim 2026 complete filter and coralife 10K with actinic blue andmoonlight lighting, as well as an extra powerhead for additional current.

I have 'wet run' my tank and all is good. I replaced all water and treated with a water conditioner. I added ~13.5 pounds of Instant Ocean 24+ hours ago and tested the salinity a moment ago. Only reads 1.012 and I am puzzled. I have a Coralife Deep Six Hydrometer that supposedly was calibrated at 75 degrees (my water is currently about 80 which I am in the process of lowering a bit). I did just read the directions and noted that I was supposed to let it sit for 24 hours with salt water in it which I have started, but my question is .... is that the reason my salinity is so low? Or is it possibly a bad hydrometer?

Thanks a million!
Nikki

[Reefland]

Hi cnpietryka,


Besides pounds, what size container of salt do you have and how much did you add? The typical 50-gallon sized bag of salt weigh about 18lbs so if have this size and didn't add nearly all of it to the tank then I would expect the specific gravity to be low. I am not familar with the Coralife hydrometer but can tell you that most of them are not accurate; some have been reported to give readings as much as .004 difference.

Secondly, I would not lower the temperature for the specific gravity check, 80 degrees F is an excellent temperature for a salty tank. I would leave it at just that.

Let us know about the salt.

[yankeebobo]

I still have the swing arms - like 3 of them. Haven't gotten out of yet but now that we're keeping the setup, that is one thing I am changing.

Anyway - As for the salt, I am going to assume that beside everything Scott mentioned, you DID stir that salt up. One thing I noticed - no matter what the bag/bucket says, and unless you put 15 power heads in, there is sediment on the bottom.

[Reefland]

Hey Bo,

Refractometers are really pretty inexpensive anymore, even the ATC models. They are worth every penny to know exactly what your salinity is and they are just as easy to use as a swing arm hydrometer.

[yankeebobo]

Originally Posted by Reefland

Hey Bo,

Refractometers are really pretty inexpensive anymore, even the ATC models. They are worth every penny to know exactly what your salinity is and they are just as easy to use as a swing arm hydrometer.

Oh I hear ya. I need to pick one and order it. After just confirming that the tank stays, I haven't gotten to that yet. But I tend to do tests with 2 or 3 of them so far to make sure they are at least off by the same amount.

[Reefland]

Originally Posted by yankeebobo

Oh I hear ya. I need to pick one and order it. After just confirming that the tank stays, I haven't gotten to that yet. But I tend to do tests with 2 or 3 of them so far to make sure they are at least off by the same amount.

Well that's reassuring.

[The R/C Man]

Hey Guys!

My swing arm was off .004. So my tanks salinity was 1.028 for a year. A refractometer is the way to go.

[Reefland]

I agree, it's a well spent $50.

[Nikki]

Thank you ALL for the information :-) Good to know about the refractometer as I am an engineer and like to know things exactly! I had an Instant Ocean bag of 15 pounds and the directios said 1.5 pounds for each 5 gallons of saltwater needed resulting in a need of 13.5 pounds. I measured it on my scale, added and was low. I have also noted with Instant Ocean if you check after 24 hours and then check again in 36 there is a change of sometimes .007 in the readings (assuming the hydrometer is consistent in its error offset).

I did stir the salt (thanks for asking though I am new to this!) and yes I always have sediment on the bottom. Hoenstly, it has been pretty discouraging to have this beautiful tank up for almost two weeks now and not even be able to get the initial salinity correct so that I can add some live rock :-(

But I aim to persevere as my daughter is asking daily when Nemo is arriving :-)

Thanks for the help and expect more newbie questions and many thanks in advance for humoring me :-)

Thanks again!
Nikki