Salt Keeps Rising

[tat2life]

any ideas why my salt level keeps rising every week/2 weeks. i change 10% water every week using straight ro water without adding any salt.. it was 1.025 when i set up tank then heater was unplugged by accident so it went right up.. added ro water til it dropped back to 1.025.. this was about 5 weeks ago and i just checked again and t up as high as the hydrometer will go. any ideas ? thanks

 

[STD]

any ideas why my salt level keeps rising every week/2 weeks. i change 10% water every week using straight ro water without adding any salt.. it was 1.025 when i set up tank then heater was unplugged by accident so it went right up.. added ro water til it dropped back to 1.025.. this was about 5 weeks ago and i just checked again and t up as high as the hydrometer will go. any ideas ? thanks

Is your hydrometer OK?

 

[tat2life]

it seems ok i checked it using just ro water, then added a tiny bit of salt to a jug and it seemed to be reading correctly

 

[aquadx]

it seems ok i checked it using just ro water, then added a tiny bit of salt to a jug and it seemed to be reading correctly

Well here are some things that might help you out:

When marine/salt water evaporates, the salt that was dissolved in the water stays in the tank. Salt can not leave a tank unless it is taken out during a water change. So, depending on the conditions in your house, your tank may be evaporating a lot and leaving its salt content with the remaining water. You may be adding properly mixed saltwater when you "top off" your tank and that may cause the rise in SG since there is already enough salt in the tank. Iif you think your tank does evaporate a lot this is something you may want to consider.

Also, water becomes more saturated (carries more dissolved salt) in certain locations when the temperatures in the tank are varied. When evaporation leaves salts behind, these salts tend to go to where its cold at the bottom of the tank or at least far from your heater if circulation is not that strong in your tank. So, keep this in mind when you take your test with your hydrometer. Try multiple locations and monitor the temperature with a decent thermometer.

Lastly, salt is not something that fluctuates by itself so this is a relatively easy problem to fix once you get the SG to where you want it. Remember, the only factors that affect salinity (SG) is temperature and how much salt you add. Just rely on good ol' trial in error!

 

[jeasko]

personally i would check hydrometer with LFS as they have a tendancy to be less accurate as time goes on, either that or speak to ski as he has a link to a site that will explain how to test/calibrate your hyrometer.

 

[SkiFletch]

personally i would check hydrometer with LFS as they have a tendancy to be less accurate as time goes on, either that or speak to ski as he has a link to a site that will explain how to test/calibrate your hyrometer.

Realm of Knowledge sticky, page 2

I agree, Verify the hydrometer first. Sure there aren't any bubbles stuck on it? If the sg was that high, you'd have lots of things dying, so chances are high it's a hydrometer malfunction

 

[yorkcoparamedic]

I got rid of my hydrometer after about 4 weeks of using it. It was always getting stuck in the highest range and constantly needed cleaned out.

I got a Refractometer they are much more accurate and very easy to use. Just calibrate it once a month with RO water to set the zero and your good to go. They range from $60 to $100 for a decent one.

 

[sophos9]

i change 10% water every week using straight ro water without adding any salt..

Something seems a bit fishey ( ) with this sentance. You do mean that you do a 10% water change with fresh salty right?

Do you top up your evaporated water every day or so?

 

[tat2life]

i do a 10% change every week using RO water... no salt added. i never need to add salt for some reason.. im guessing because the water level drops and salt stays in.. wich i didnt know so thanks for telling me that. i top up the tank every week when i do water change using RO water again no salt because it always rises within a week. as soon as i add RO water it drops back down to around 1.026 then a week later its right back up again. all the fish seem ok, my zoas died .. well dissaperd into the rocks just faded away.

 

[Donya]

I agree with sophos9 here; unless I'm misinterpreting your descriptions, something sounds really strange. When do a water change, are you are taking X amount of water out that contains salt, putting X amount of RO back in, and never adding salt any other time to the tank? If not and you're actually putting X amount of sea water back in (what you should be doing), then maybe you need to top up more frequently. If, on the other hand as it sounds from your descriptions, you're putting X amount of RO back in and truely never adding salt back to the tank, your salt is going down regardless of what the hydrometer says. Hydrometers can also be affected by more things than salt...you can get a high sg reading from water saturated with calcium carbonate that has no salt at all in it.

 

[Lost_Jock]

Based on my hydrometer / maintenance my SG levels are rising for no reason, despite my hydrometer being only a few months old. I understand that evapouration increases SG and that plain water tap-ups restore the original balance.

I have 2 x 250w heaters in the sump of a 66g tank and the temp varies between 25.0 - 25.5'C. I have just changed my skimmer from a berlin air-pump 90 to a mce600. Water changes are done with the same SG level as the tank and top-ups are done with plain water @ 1.5ltrs p/d (evaporation). In my view the SG levels should remain constant, although according to my hydrometer they are increasing.

Questions
1) Are there other factors that could affect SG readings with a hydrometer other than calcium levels?
2) Does a refractometer take account of the calcium levels, to give a pure SG reading (irrespective of calcium)?
3) Is a refractometer really worth the extra cost / maintenance?

Thx, Mark

 

[Donya]

I have 2 x 250w heaters in the sump of a 66g tank and the temp varies between 25.0 - 25.5'C. I have just changed my skimmer from a berlin air-pump 90 to a mce600. Water changes are done with the same SG level as the tank and top-ups are done with plain water @ 1.5ltrs p/d (evaporation). In my view the SG levels should remain constant, although according to my hydrometer they are increasing.

If it's slowly increasing with the new WC water being the same sg and topoffs of RO, you could need more topoffs or your hydrometer might need a cleaning.

Are there other factors that could affect SG readings with a hydrometer other than calcium levels?

Yes - mix up a solution saturated with baking soda (sodium bicarbonate) and you can push it right off the scale. The float responds to relative density of the fluid, so anything that increases the density will raise the sg. It's been a long time since I've had access to a refractometer, so I will have to let someone else take those. Based on my experience with non-aquarium refractometers in chemistry labs, I would think more things than just salt could affect the reading than salinity (although maybe not significantly), but then again I'm not sure what exactly how the digital refractometers take their measurements.

 

[SkiFletch]

Answers:

1) Are there other factors that could affect SG readings with a hydrometer other than calcium levels?\

- yes, bubbles on the tip, or one that was left to dry out without being first rinsed in freshwater. "affordable" hydrometers are notorious for drifting bad over time, hence my suggestion to all to verify/calibrate theirs often.


2) Does a refractometer take account of the calcium levels, to give a pure SG reading (irrespective of calcium)?

- At seawater concentrations yes. Remember, seawater contains salt in concentration of 35 parts per THOUSAND, while seawater's calcium concentration is ~400 parts per MILLION. That means that there is almoast 100 times as much salt in seawater than there is calcium (or carbonate/alkalinity for that matter). Furthermore, typical fluctuations in calc/alk/mg are only on the hundred or so of parts per million. Which is MUCH less than the concentration of salt (less than 1%), thus changes in these ions in relatively normal concentrations of seawater will NOT affect the reading of a refractometer.

What Donya says is true, but remember a saturated solution of freshwater and carbonate again contains carbonate levels in the parts per thousand, not parts per million like is in our seawater


3) Is a refractometer really worth the extra cost / maintenance?

- IMO, yes. They do not drift over time and are actually easier to maintain. Just a drop of water on the lens, snap the cover down, read/record the sg, snap cover up, quick rinse in fresh or RO/water by just dipping or quickly running under a tap and it's all done. No monkeying around with bubbles on the needle, thorough rinsing, etc. refractometers are much easier to operate IMO.

 

[Lost_Jock]

Thx Donya & SkiFletch

Got another hydrometer today to test out, as there pretty inexpensive. This proved it was snookered.

Looks like a refractometer. Is there any you could recommend in the UK?


Appreciated, Mark

 

[SkiFletch]

Just about any one you can find . The cheaper ones ~30quid its a good idea to run a verification/calibration with a home-made solution to make sure they're right. Once calibrated though (they come with an adjustment for it), it will be reliable and accurate across the range you're reading. Calibrating at 0ppt (RO water) is a bad idea, since the cheap ones tend to drift the further you get from the cal point, so by the time you're at 35ppt it may be a little bit off. Make sense?

The more expensive models ~60-80+ won't require cal and will prolly work just fine out of the box