Silly Hydrometer Question

[Dadof4]

There's also not much wrong with weighing out salt to a known volume of water. So I don't think your's is a silly Q. If not for any other reason, I like to check tank salinity to check for evap losses. Just belt and braces - by weighing, you know what it should be. By using a device like these, you measure the actual salinity.

Also, the salinity you get seems to change for a given weight of salt and volume of water depending on the brand of salt. One brand I have used, seems to give less than I would expect.

Then there is water absorbtion, by salt. Not a massive problem, but given a chance, salt in a bag or bucket will pick up whatever water it can from the air if nowhere else but you'd have to leave something open to damp for weeks to really have a problem. It forms hard clumps and leaks seawater, eventualy, if you have not seen it this way. But I've also used salt that looks fine but I get less salinity for the weight than I should or as written on the box.

One last thing, I've found with one brand of salt, different from the last brand was that I get a massive nitrite reading in my mixing tank if I leave it mixing for three days onward. Sometimes, I think that's due to bits of seaweed I can see in it as it dissolves. Up to two days mixing seems fine and 24 hrs mixing and aeration seems to be recomended.

Just passing on what I've found with mixing salt (snore)!

[Dadof4]

There's also not much wrong with weighing out salt to a known volume of water. So I don't think your's is a silly Q. If not for any other reason, I like to check tank salinity to check for evap losses. Just belt and braces - by weighing, you know what it should be. By using a device like these, you measure the actual salinity.

Also, the salinity you get seems to change for a given weight of salt and volume of water depending on the brand of salt. One brand I have used, seems to give less than I would expect.

Then there is water absorbtion, by salt. Not a massive problem, but given a chance, salt in a bag or bucket will pick up whatever water it can from the air if nowhere else but you'd have to leave something open to damp for weeks to really have a problem. It forms hard clumps and leaks seawater, eventualy, if you have not seen it this way. But I've also used salt that looks fine but I get less salinity for the weight than I should or as written on the box.

One last thing, I've found with one brand of salt, different from the last brand was that I get a massive nitrite reading in my mixing tank if I leave it mixing for three days onward. Sometimes, I think that's due to bits of seaweed I can see in it as it dissolves. Up to two days mixing seems fine and 24 hrs mixing and aeration seems to be recomended.

Just passing on what I've found with mixing salt (snore)!

When you raise your SG it is important to raise by .002 or less. The bacteria does not tolerate a stonger increase. All cells have sodium, potassium and water with in a semi permiable membrane wall. The water stays in the cell because of sodium and potassium's affinity for water. If you increase the sodium and potassium content in the water outside the membrane wall to a higher concentration than what is inside the membrane, you will cause the water to be drawn out of the cell, killing it. There is normal water and ion movement across the cellular membrane so a slight (less than .002)increase in the outside ion content doesn't affect the water in the cell. I am trying to capture this process on video under the microscope to show how fast this happens but for some reason I can't get my video out from the microscope to work.

[Jivenjune]

I've had success with Instant Ocean's hydrometers when compared to a calibrated refractometer, so I can't speak for any other brand but Instant Ocean. When measuring my salinity from brackish to marine, it turned out to be surprisingly accurate as long as there were no bubbles lodged in the hydrometer (just tap it in the water a few times). The Instant Ocean hydrometer gave the exact same SG value as my refractometer regardless of varying salinity levels. Pretty decent deal for like eight bucks? Most of the pet stores in my area seem to use the Instant Ocean one, too.

[soggydrysuit]

Hi schismy007,

Sorry, must have you mixed up with someone else. I went looking for where I thought I saw an ad for 3 gsp's looking for a new home. Where I got the number 4 from - pass.

Just found another an ad for another 3 small gsp's for 4 ukp each. Bit depressing really, they are being dumped so readily. (but not by you).

Maybe if you pm a moderator, they could let you change your name and keep the rest of your profile? I've been on this forum intensively for less than a week and i'd twig who you were from your extensive stock list!

Hi dadof4,

That would be most interesting to watch at some point. I've captured polymers crystallising before, down an optical mic (environmental SEM probably wouldn't work for obvious reasons), but I'd have to rig a camera to use on my own microscope to get around the H+S at work!

Good luck and sorry for any confusion - it appears to be a forte of mine!

[soggydrysuit]

Interesting: if it's not broken, don't fix it...

I just break glass hydrometers!

[soggydrysuit]

There's an interesting acticle on hydrometers and temp corrections here (http://reefkeeping.com/issues/2004-07/rhf/index.php). It's probably more useful for people who keep reefs who need to know what their salinity actually is. Probably for me and my brackish puffs, I'd just want to know roughly and that I hadn't increased the salinity too far

Sounds like the swing arm ones don't really need correcting, if you can get rid of bubbles.

[pufferpuggirl]

The one I bought came with a little stick and I just tap around inside the hydrometer with the stick and the bubbles go away. Works okay for me. And I'm like you Soggy ... I don't need exact measurements with just the few brackish tanks I have, so I think I will stick with the swing-arm hydro for now.