What is my Specific Gravity!?! AGH!!!

[JaredCBell]

So using a deep six hydrometer, My SG measures out to 1.025-6. Not sure if my hydrometer was off I devised a small experiment to make sure that it was correct.

I dissolved 1/2 cup of marine salt which I use in a 1 gallon container. The package says this should create a SG of 1.023. So when I tested it, it came out to 1.018.... Wanting to make sure even more, I took my hydro to petco and tested their water. Same thing, 1.018.

Freaking out because now my SG is probably WAY too high, I bought another hydro but this time a bobbing one (from like the 70's, haha). Read the instructions. It said to keep the SG within the "green" zone on the hydro. So I tested in my aquarium and it was almost in the MIDDLE of the green zone, maybe a little bit higher in SG.

i really cant buy a refractometer right now but Im just hoping Im not killing my live rock or anything.

yet my figure 8 puffers and green green spotted puffers are doing exceptionally well. i still cant figure out why people say the figure 8 is fresh water only and to acclimate the GSP to full marine when its an adult. its still a baby and he is lovin life!

[unleashed]

Your rock should be fine for now, but I strongly believe that you should invest in a refractometer ASAP. Even relatively cheap refractometers are generally much more accurate than hydrometers.

I bought one off of marine depot on sale for about $30USD that was a couple of years ago and it's still as accurate as the day I bought it

[JaredCBell]

Your rock should be fine for now, but I strongly believe that you should invest in a refractometer ASAP. Even relatively cheap refractometers are generally much more accurate than hydrometers.

I bought one off of marine depot on sale for about $30USD that was a couple of years ago and it's still as accurate as the day I bought it

well when I want to start adding fish, will they be fine? So many people have been successful with just hydros!

[unleashed]

That's a hard question to answer as I don't know what your actual specific gravity is. Some fish will be fine with a high SG, others not. I know that in the Red Sea, the SG can get as high as 1.030 especially during summer towards Egypt etc.

The problem is that you are getting different readings which is why I cannot accurately answer your question.

Also, many LFS will keep their fish tanks between 1.018 and 1.027, depending on the store. This mainly has to do with reducing disease etc. However, see what SG their coral tanks are as inverts generally need to be kept between 1.024 and 1.027 for long term health and then calibrate the result for your tank.

Again, I strongly recommend that you invest in a refractometer as these are extremely accurate if used properly

[ILuvMyGoldBarb]

At the very least you need to have someone with a calibrated refractometer test your water. Once they test it, test it with one of your hydrometers and compare the difference. Then each time you test using the hydrometer, take that difference into account. The only downside to this is that the swing arm style hydrometers will change. Just for example, I have a coralife hydrometer and a refractometer. My refrac is obviously dead on, however if I test with the hydrometer, I have to add .005 to the test. So water that tests at 1.025 with my refrac will test at 1.020 with my hydrometer.

[JaredCBell]

I really dont want to spend more than 30 on one. Anyone got any suggestions? Deals?

what about this guy:
[Only Registered Users Can See Links.]

[unleashed]

That one should be fine as long as you properly calibrate it

[JaredCBell]

That one should be fine as long as you properly calibrate it

argh. off to do more research! (blush)

[unleashed]

It should come with instructions for calibrating it.......

[kaybee]

Buy some Salinity Calibration Fluid which will enable you to calibrate against a known salinity (which is more accurate than calibrating to zero using distilled or ro/di water).

I also recommend anyone who uses a refractometer to calibrate at least monthly as refractometers lose they're accuracy over time. I made the recent mistake of going a very long span without regular calibration and discovered the SG in my tank was 1.038 rather than 1.025! :exclaim:

[kaimarkhirst]

30 quid wil lbuy you a fairly decent one.

Ive got this one for £29.99 and its fantastic I can tell you. The shop calibrated it for me, and it precise and very easy to use...

[Only Registered Users Can See Links.]

[ILuvMyGoldBarb]

I've talked to people who have $30 refracs and $200 refracs and they say that the $30 model is just as good and just as accurate as the $200. The only difference may be the frequency that you need to recalibrate them.