Salinity Dropped from 1.024 to 1.018 overnight.

[subie]

Hi all,
Last night my 65 Gallon tank was doing great, everything was running perfect. I woke up this morning and noticed the salinity in my water dropped from 1.024 to 1.018 overnight. I looked for a leak even though my water levels never changed. It could just be a faulty hydrometer but last night it was giving me accurate readings so now I'm just confused. Any input helps!

 

[Crabs McJones]

Welcome to R2R!
Do you know if your auto top off got stuck on? Is your reservoir empty? Otherwise I wouldn't trust your hydrometer. Best bet would be to invest in a good refractometer

 

[W1ngz]

Salinity doesn't just change. If the water level is constant, the only way to truly lower the salinity is to remove salt water and replace it with fresh water.
Hydrometers are notoriously inaccurate and flaky. The slightest air bubble stuck to the pointer can cause a reading to be off by several points.

The inverse is also a possibility, that last night's 1.024, while a desirable number to see, may be the inaccurate one and the 1.018 is the accurate number. A bit of encrusted salt stuck to an improperly cleaned hydrometer would cause that.

Ditch the hydrometer and get a refractometer and calibration solution to get accurate readings.

 

[NWJerseyReefer]

I agree with the above mentioned. Hydrometers are extremely inaccurate and salinity is a perimeter that you want consistency with all the time. Invest in a refractometer. Extremely accurate, cheap, and quick. Bought mine on amazon for maybe 15 bucks

 

[Sailingeric]

If you know how much salt you are using in your water, and you have line or something marked for your water level in your sump, it should not change much, maybe a little from salt creep but if you put it back in your tank, the change would be negligible.

I have a line on my sump and thanks to it I found out my ATO was siphoning when I filled up my reservoir, not by much but enough to know I needed to fixed it.

 

[subie]

Welcome to R2R!
Do you know if your auto top off got stuck on? Is your reservoir empty? Otherwise I wouldn't trust your hydrometer. Best bet would be to invest in a good refractometer

Looking at the replies, I'll invest in a refractometer and see the results from it. Thanks for the help everyone.

 

[acro-ed]

I've seen this several times with hydrometers (usually a tiny bubble in just the wrong spot). I also had a refractometer recently that wouldn't work properly. I calibrated it again and the readings were still inconsistent. I then re-calibrated another one, checked multiple times, and consistently got the reading I expected initially. Point being, if you have an outlier reading (on anything: salinity, alk, whatever) double check it first before taking action. No real explanation on why a seemingly good instrument would give wildly inconsistent readings.

 

[LesPoissons]

You only have 2 options:
1. Faulty hydrometer
2. Too much fresh water was added to the tank. Check your ato level. If it got stuck, if a siphon is created, if algae is blocking your overflows etc.

 

[OpenOcean33]

Welcome to R2R!
Do you know if your auto top off got stuck on? Is your reservoir empty? Otherwise I wouldn't trust your hydrometer. Best bet would be to invest in a good refractometer [/QUOTEA. I agree with this, hydrometer meters tend to get stuck, usually with air bubbles or something to throw it off, I would definitely recommend the BRS refractometer, cheap and work great, and most of all reliable.

 

[Ralph Ritoch]

Hi, I'm a complete newbie so take everything I say with a grain of salt BUT the hydrometer measures specific gravity, it doesn't measure salinity. It is an indicator of salinity. For better or worse I recently added 2 tums to my tank to provide calcium to my torch corals, which were dying before I even added them to my tank. After adding the tums it lowered the SG from 1.023 to about 1.021. There is no way 2 small tablets in a 40 gallon tank lowered the salinity by a measurable amount but it could have introduced chemicals with a very low density. It seems unlikely that your salinity changed, what changed is the the density of the water in your tank. My newbie suggestion is from Hitchhikers guide to the galaxy, don't panic. Add some reef salt to be safe but it is most likely something else that is low density that entered your tank and caused the drop. In my case it was Tums.

 

[W1ngz]

Hi, I'm a complete newbie so take everything I say with a grain of salt BUT the hydrometer measures specific gravity, it doesn't measure salinity. It is an indicator of salinity. For better or worse I recently added 2 tums to my tank to provide calcium to my torch corals, which were dying before I even added them to my tank. After adding the tums it lowered the SG from 1.023 to about 1.021. There is no way 2 small tablets in a 40 gallon tank lowered the salinity by a measurable amount but it could have introduced chemicals with a very low density. It seems unlikely that your salinity changed, what changed is the the density of the water in your tank. My newbie suggestion is from Hitchhikers guide to the galaxy, don't panic. Add some reef salt to be safe but it is most likely something else that is low density that entered your tank and caused the drop. In my case it was Tums.

Don't add tums to your tank... it doesn't have heartburn. Stop taking the advice of whomever told you it was a good idea.

Tums is calcium carbonate held together with sodium. When the sodium dissolves, the calcium carbonate may become free in the water column, but probably settle. Either way it's not usable by your corals as it won't separate the calcium from the carbonate without being in a more acidic (lower ph) solution. Calcium carbonate is the same thing reef rock and coral skeletons are already made of. Calcium additive is Calcium Chloride which produces calcium hydroxide and hydrogen gas after it reacts with water.

The differences between specific gravity and salinity are real, but the measurement is the same and any difference is negligible for the needs of a reef tank.

 

[Ralph Ritoch]

Don't add tums to your tank... it doesn't have heartburn. Stop taking the advice of whomever told you it was a good idea.

Tums is calcium carbonate held together with sodium. When the sodium dissolves, the calcium carbonate may become free in the water column, but probably settle. Either way it's not usable by your corals as it won't separate the calcium from the carbonate without being in a more acidic (lower ph) solution. Calcium carbonate is the same thing reef rock and coral skeletons are already made of. Calcium additive is Calcium Chloride which produces calcium hydroxide and hydrogen gas after it reacts with water.

The differences between specific gravity and salinity are real, but the measurement is the same and any difference is negligible for the needs of a reef tank.

I was the idiot who thought of adding the Tums. Its the only calcium source I have readily available. I dissolved it first and then poured it in. The tank was cloudy for a few hours but didn't do any damage. The Torches seemed to really like it, the healthy ones fully extended and even some of the sick ones partially extended. I don't intend to do it again, but I may add a calcium reactor which seems to be a good long-term solution.

 

[W1ngz]

I was the idiot who thought of adding the Tums. Its the only calcium source I have readily available. I dissolved it first and then poured it in. The tank was cloudy for a few hours but didn't do any damage. The Torches seemed to really like it, the healthy ones fully extended and even some of the sick ones partially extended. I don't intend to do it again, but I may add a calcium reactor which seems to be a good long-term solution.

I'd hardly use the word idiot! It's a newbie mistake, we all made many and so will you.
Welcome to the eternal chemistry lesson that we all call 'reefing'!

 

[MattR]

@subie Just bought a refractometer on Amazon for cheap and it's extremely accurate, PM me and I can show you which if you are interested

 

[Ralph Ritoch]

Hi all,
Last night my 65 Gallon tank was doing great, everything was running perfect. I woke up this morning and noticed the salinity in my water dropped from 1.024 to 1.018 overnight. I looked for a leak even though my water levels never changed. It could just be a faulty hydrometer but last night it was giving me accurate readings so now I'm just confused. Any input helps!

I have recently run into a similar problem and I have a theory. Yesterday I tested the salinity of the tank and it was 1.020 so I added some salt until the hydrometer read 1.022. Today I tested again and the salinity is back down to 1.020 again so I added more salt until it read 1.022. About 30 minutes later I retested and it was back down near 1.020 again. My theory is that I didn't add enough salt and that my initial reading was higher because the salt hadn't fully ionized (dissolved).

 

[W1ngz]

....so I added some salt

Don't add salt directly to your tank. Dissolve the salt properly in a bucket of water to create some water say, 1.030 or 1.040 and use that to do a water change.

This calculator will help you create a water change schedule that will increase salinity to a specific target.

Target Salinity Calculator

Aquarium calculator; Create a water-change schedule that can be used to reach a target salinity.

www.hamzasreef.com

Also, 1.020 to 1.022 is well within the kinds of errors that hydrometers are known for. A refractometer or digital meter and calibration solution would be a worthwhile investment.

 

[Ralph Ritoch]

Don't add salt directly to your tank. Dissolve the salt properly in a bucket of water to create some water say, 1.030 or 1.040 and use that to do a water change.

This calculator will help you create a water change schedule that will increase salinity to a specific target.

Target Salinity Calculator

Aquarium calculator; Create a water-change schedule that can be used to reach a target salinity.

www.hamzasreef.com

Also, 1.020 to 1.022 is well within the kinds of errors that hydrometers are known for. A refractometer or digital meter and calibration solution would be a worthwhile investment.

Thanks for the tips. What I actually have been doing is taking a bowl of tank water, adding salt to that and stirring. Once the salt appears to be dissolved I pour it back into the tank. The salinity read by the hydrometer of the actual ocean water is about 1.018 but its collected within a mile of a river so that is probably why it comes in low. Next water change I'll try to raise its salinity to the high range for a reef (1.025) and look into refractometer/digital solution.

 

[W1ngz]

....... its collected within a mile of a river so that is probably why it comes in low.

You're not concerned about runoff and pollutants near the mouth of a river? There's a high chance you have all kinds of stuff from raw sewage to pesticides, nitrates and phosphates from agricultural land.

 

[landlubber]

Don't add salt directly to your tank. Dissolve the salt properly in a bucket of water to create some water say, 1.030 or 1.040 and use that to do a water change.

This calculator will help you create a water change schedule that will increase salinity to a specific target.

Target Salinity Calculator

Aquarium calculator; Create a water-change schedule that can be used to reach a target salinity.

www.hamzasreef.com

Also, 1.020 to 1.022 is well within the kinds of errors that hydrometers are known for. A refractometer or digital meter and calibration solution would be a worthwhile investment.

agreed on all points.
to further this it should be pointed out that while salt seemingly dissolves in 15 mins to appear ready to be added it shouldn't. the pH of the new water will be considerably lower than your system water and could cause an abrupt shock. I usually give it at least 4 or 5 hours (or overnight) of mixing to stabilize the pH and temperature correct.
Even after all that precaution you still want to raise the salinity slowly via using the saltwater as your ATO source or by manually topping off. 2 or 3 days later things will be back to good and your fish/corals will have suffered minimal stress.

 

[Ralph Ritoch]

You're not concerned about runoff and pollutants near the mouth of a river? There's a high chance you have all kinds of stuff from raw sewage to pesticides, nitrates and phosphates from agricultural land.

I'm in a fishing town in the Philippines. I don't believe there are pesticides or raw sewage in the river. The nitrates and phosphates may be high but the water is collected about a mile from the mouth of the river. They are fishing shrimp directly out off the river for food so it seems unlikely the human contamination of the river water is high enough to hurt the fish. Bacteria is very high in the water and kills most aquariums here so I've added a UV sterilizer. So far, no deaths.