Salinity question...

[Hemmdog]

I’m probably not waiting long enough to take a reading of my mix. I take the reading at 2 hours of mixing and that’s it...

Your bringing it up to the same temp as the tank right? Cold saltwater will read differently on a refractometer than warm saltwater.

 

[W1ngz]

I’m probably not waiting long enough to take a reading of my mix. I take the reading at 2 hours of mixing and that’s it...

My money is on refractometer. Definitely get some 35ppt solution. Keep in mind that stuff does expire and eventually will have to be replaced, but that's about a year down the road.
If you suspect insufficiently mixed water, are you mixing by hand? Use a cheap maxijet pump to keep it moving around. What color bucket are you mixing in? Not that the color of the bucket will change the mixing time, but anything other than a white bucket will let you see if there is salt on the bottom before you take the readings.

Do you dump the whole 2.5-3 cups of salt in one plop when you mix? I usually prefer to shake the salt out slowly so that a lot of it gets dissolved in the spiral down, and doesn't pile up.

I'd think 2 hours is lots of time to get an accurate salinity reading, regardless of temperature. After about 30 seconds on the prism, your 3 drops of water are going to be the same temperature as the glass.

 

[Haroldeez]

Your bringing it up to the same temp as the tank right? Cold saltwater will read differently on a refractometer than warm saltwater.

Yes my RO supply is heated

 

[Haroldeez]

My money is on refractometer. Definitely get some 35ppt solution. Keep in mind that stuff does expire and eventually will have to be replaced, but that's about a year down the road.
If you suspect insufficiently mixed water, are you mixing by hand? Use a cheap maxijet pump to keep it moving around. What color bucket are you mixing in? Not that the color of the bucket will change the mixing time, but anything other than a white bucket will let you see if there is salt on the bottom before you take the readings.

Do you dump the whole 2.5-3 cups of salt in one plop when you mix? I usually prefer to shake the salt out slowly so that a lot of it gets dissolved in the spiral down, and doesn't pile up.

I'd think 2 hours is lots of time to get an accurate salinity reading, regardless of temperature. After about 30 seconds on the prism, your 3 drops of water are going to be the same temperature as the glass.

I use a return pump to mix, and I also just dump in a bit at a time no more than a cup sprinkled in at a time. I wait 15 seconds after I drop the refractometer door to read

 

[Haroldeez]

My money is on refractometer. Definitely get some 35ppt solution. Keep in mind that stuff does expire and eventually will have to be replaced, but that's about a year down the road.
If you suspect insufficiently mixed water, are you mixing by hand? Use a cheap maxijet pump to keep it moving around. What color bucket are you mixing in? Not that the color of the bucket will change the mixing time, but anything other than a white bucket will let you see if there is salt on the bottom before you take the readings.

Do you dump the whole 2.5-3 cups of salt in one plop when you mix? I usually prefer to shake the salt out slowly so that a lot of it gets dissolved in the spiral down, and doesn't pile up.

I'd think 2 hours is lots of time to get an accurate salinity reading, regardless of temperature. After about 30 seconds on the prism, your 3 drops of water are going to be the same temperature as the glass.

I’m gonna order calibration fluid today

 

[Haroldeez]

I’m gonna order calibration fluid today

Oh also i do somewhat add routine water changes.... 5 gallons every other day. I find it quite easy

 

[Hemmdog]

Oh also i do somewhat add routine water changes.... 5 gallons every other day. I find it quite easy

You unplug your ato when you do these water changes right?

 

[w2inc]

Answer to your question is no. It is not normal to have your salinity drop. Conceptually it is not really possible for your salinity to drop from evaporation. 35 down to 30 in 4 days means that you lost 14% of your salt some place.

Sounds like you have a good refractometer. However, there is still a chance that it is not reading correctly. Have the LFS check your salinity and your meter to be sure that they are getting the same results. Get a bottle of salt water from your tank when it is at 35 and seal it up. When the salinity in your tank drops, check the salinity of the water in the bottle and see if it is still the same. That would help you rule out your meter.

I feel like you would know if you had a leak in the tank, but if your home is dry enough to evaporate a gallon a day then there is still a chance that there is a leak you haven't spotted. Just not a very good chance. How many gallons is the tank? We can take a look at how many gallons of water you are putting in compared to your tank size and salinity drop to get a better idea. A leak would lose salt and water at the same rate. Account for evaporation and you should lose proportionally more water than salt if you may still have a leak. If the salt loss is equal to or more than the water loss proportionally, then you have something else.

Are you sure we can rule out the skimmer? Is there a situation that might be causing the collection cup of the skimmer to be evaporating really fast? Tons of warm dry airflow going through the skimmer collection cup blowing on your skimate? If it looks like it isn't doing much, then turn it off for a couple days and see if the salinity still drops. If your neighbor has a similar phenomenon, maybe it is something more subtle like that.

It is worth tracking down. It will be tough to keep coral if you don't have control of your salts.

 

[RobW]

red sea pro.... why I’m using pro I have no idea I don’t plan on corals till months and months from now. I’ve basically just been getting the most expensive of everything thinking it must be the best

Good salt... I'd just keep using it if you're going to eventually do corals. Brightwell Neo-Marine Salt is good too.

 

[RobW]

How are you adding your salt? Do you mix your salt in water first and let it do its thing for a while before adding to the tank? Or do you add salt directly to the tank?

 

[Haroldeez]

How are you adding your salt? Do you mix your salt in water first and let it do its thing for a while before adding to the tank? Or do you add salt directly to the tank?

I mix it in a barrel for 2 hours

 

[Haroldeez]

You unplug your ato when you do these water changes right?

Lol yup

 

[Ferrell]

I notice from the apex graphs that mine will vary about 0.5 between water changes (every other Sunday) and seems to balance out at about 34.5. Can never keep at 35. I also use about a gallon every 24 hrs on a 75/20 but never see a 4 point drop. Must be going somewhere, trying not to be redundant, but sounds like a leak. Good luck

 

[lapin]

Hi and thank you, it’s been set up about 2 months and it drops from 35ppm to 30 about every 4 days. Yes topping off with freshwater ATO about a gallon a day

Haven’t had to dump my skimmer cup yet lol it’s a fairly new tank

To have a salinity drop in water you need to remove salt. You say you have no salt creep. If your testing method and device are accurate, then you must be removing salt water and replacing it with water of a lower salinity to cause the drop. This is a law of physics we can not debate.
2 hours of mixing Red Sea salt with a strong pump will have it all mixed unless it has been exposed to moisture and is clumped up.
I would check the salinity of your mix and tank right before the water change. Then check the tank right after. Be sure to clean your refractometer and pipette with rodi water between tests.

 

[BeejReef]

Your bringing it up to the same temp as the tank right? Cold saltwater will read differently on a refractometer than warm saltwater.

Did not know this

 

[vetteguy53081]

Salinity should be increasing with evaporation. I would take your instrument that you use to check, to a local LFS and have them compare with theirs. While at it, take a water sample along and have them test with their unit to compare readings