Bogus hydrometer readings.

[easyian]

Does anyone know of something you can test your hydrometer with? Say like a common food liquid that has a specific gravity? The problem i just ran into was salinity levels way off the chart. I was pluging along with my tank for the last year and a half, assuming(my first mistake) that my hydrometer was correct. the only reason I questioned it was when i was making water for my last water change i forgot how much salt i had put in the bucket. So after i mixed it I floated my hydrometer and it read low. No matter how much salt i added it didn't change. So there I stopped. Today was the first day I could get to the LFS and I got myself a new hydrometer. I decided to buy the style you fill and it has a little pointer inside. I got it home and tested my tank and it had to be close to Dead Sea levels because it was so high it pegged the needle full at the top, past 1.032 sg. So out came the bucket and i did a little water change and brought the salinity down to 1.024 sg. I'm a little ashamed of myself and feel like slapping my own hand. So what I want to find is something that has a set specific gravity so I can test my hydrometer until I can afford a refractometer.

 

[ClamKnuckle]

The specific gravity of pure water is one (better be since thats how we calibrate stuff at work), so if you have some pure water that would be a good reference i guess. I'm no scientist but I would assume RO/DI would work better then tap. Someone else will probably have a better answer for you though!

I had problems with my hydrometeor with the little needle in it...reading low off the charts, so I'm not sold on them either. I have to get a refractometer too!

edited...was reading low not high

 

[MT79]

I don't know of anything but water which is obviously 1.000. Plastic hydrometers are infamous for reading low, IME. I still use a plastic hydrometer but I keep my water at 1.024 to give some buffer on the actual sg. I plan on buying a refractometer ASAP, I suggest the same for you. Good luck.
PS- floating hydrometers should be atleast 12 inches long to be accurate I've read.

 

[1neondottyback]

Dropping your SG that fast could do more harm than good if the SG slowly crept up to those levels. Fish could go into shock as well as your corals. I thought natural sea water was closer to 1.027 or 35ppt. Some reefs do go as high as 41 ppt like the Red Sea. You guys keep your SG low to battle ich? What temp do you keep your tank?

Remember when you use the floating type hydrometer SG readings are effected by temp. They are calibrated for a specific temp, floating type. That is why the refractometers are so highly prized, more accurate and not affected by temp. Please correct me if I am wrong..

 

[1neondottyback]

The higher the SG around 1.027 is actually good for coralline growth. Like temp fish can get more aggressive with higher levels of SG. The osmosis factor kicks in and it's harder for fish to breathe through lateral line and scales.

 

[fishfreek]

For accuracy nothing beats a refractometer. If you know someone in your area who has one they will probably be more than willing to help you calibrate your swing arm hydromoter by finding out how far off it is. I have heard reports of some being as far off as .01 so a 1.025 tank would read 1.015. Most are closer to .005 off so a 1.025 would be 1.020.

 

[RocketSeason]

perhaps getting another hydrometer and comparing the readings there? If your LFS uses a refractometer, why not bring in some water from home?