Salinity dropping slightly

SurfLife · May 16, 2018

220G , open top, sump in basement.

I try to keep the salinity around 1.027. After about 7-10 days it will get down to around 1.024-025(Have not seen it go any lower than that).
I keep a container of RO water that the ATO pulls from.
My understanding early on was that water evaporates but the salt does not. I do have a very small amount of salt that collects around the sump etc but otherwise stays fairly clean.
My ATO replaces roughly 2 gallons a day.
Anything to be concerned about or just keep a closer eye on it and keep it from dropping?

Brew12 · May 16, 2018

SurfLife said:
220G , open top, sump in basement.

I try to keep the salinity around 1.027. After about 7-10 days it will get down to around 1.024-025(Have not seen it go any lower than that).
I keep a container of RO water that the ATO pulls from.
My understanding early on was that water evaporates but the salt does not. I do have a very small amount of salt that collects around the sump etc but otherwise stays fairly clean.
My ATO replaces roughly 2 gallons a day.
Anything to be concerned about or just keep a closer eye on it and keep it from dropping?

I feel that is something to be concerned about. There is a little salt that gets trapped in the water when it evaporates, but it shouldn't be significant. How much skimmate are you pulling out?

Bayareareefer18 · May 16, 2018

Brew12 said:
I feel that is something to be concerned about. There is a little salt that gets trapped in the water when it evaporates, but it shouldn't be significant. How much skimmate are you pulling out?

+1

When I was trying to get my skimmer tuned it was pulling out a lot if water. Replacing that with RODI caused a drop in salinity over time

mitch91175 · May 16, 2018

Wow 2 gallons a day that is a lot of water. What is your temp? Check that skimmer so it won't pull so much water out. Your salinity shouldn't fluctuate like that.

mitch91175 · May 16, 2018

Also what are you using to test your salinity? If using a refractometer (I use a Milwaukee), you need to calibrate it using RO/DI water first then you can test your salinity.

smokin'reefer · May 16, 2018

I had a similar situation with salinity level dropping. It took about a month and then I found a leak under my tank. This might not be your issue but something you might want to keep an eye out for.

Good luck and happy reefing.

SurfLife · May 17, 2018

Bayareareefer18 said:
+1

When I was trying to get my skimmer tuned it was pulling out a lot if water. Replacing that with RODI caused a drop in salinity over time

This may be what is causing it. My experience with a skimmer only goes back to Feb so I am not real sure at this point what is a lot. It does pull quite a bit(imo) and could probably be turned down to reduce the water ratio of the skimmate. I will try that first.

I checked Salinity last night and it read 1.026 after 6 days(1.027 start).

SurfLife · May 17, 2018

mitch91175 said:
Also what are you using to test your salinity? If using a refractometer (I use a Milwaukee), you need to calibrate it using RO/DI water first then you can test your salinity.

I also use Milwaukee and calibrate it regularly as it only takes a second.

Halal Hotdog · May 17, 2018

If you can calculate the amount of salinity drop per day then you can adjust your ATO water to have a little salt in it. Also I am a fan of wet skimming myself, and this is how I compensate.

SurfLife · May 17, 2018

Halal Hotdog said:
If you can calculate the amount of salinity drop per day then you can adjust your ATO water to have a little salt in it. Also I am a fan of wet skimming myself, and this is how I compensate.

OK so you are verifying that 'wet' skimming will have this effect. Thank you. I considered your solution but wanted to get opinions first. I am going to start by making small adjustments to my skimmer while testing daily to see what effects it has. It wouldn't hurt to spend a little time getting more familiar with my skimmer.

Bayareareefer18 · May 17, 2018

SurfLife said:
OK so you are verifying that 'wet' skimming will have this effect. Thank you. I considered your solution but wanted to get opinions first. I am going to start by making small adjustments to my skimmer while testing daily to see what effects it has. It wouldn't hurt to spend a little time getting more familiar with my skimmer.

It's taken me over a month to get my skimmer tuned. Doesn't help that I don't have any bioload yet. I found that tiny little adjustments need to be spaced really far apart. I made the error of over adjusting too frequently

samnaz · May 17, 2018

What about salt creep?

Halal Hotdog · May 17, 2018

SurfLife said:
OK so you are verifying that 'wet' skimming will have this effect. Thank you. I considered your solution but wanted to get opinions first. I am going to start by making small adjustments to my skimmer while testing daily to see what effects it has. It wouldn't hurt to spend a little time getting more familiar with my skimmer.

Yes wet skimming can lower your salinity if your ATO is replacing the water with pure RO/DI water. Also typically there is no harm in turning off your skimmer for one week. If you suspect there maybe a leak or other issue, then turn off the skimmer and monitor your salinity for any drop. Salt creep can affect salinity, but typically is nothing significant unless you have mounds of it building up in a very short period of time.

SurfLife · May 18, 2018

Bayareareefer18 said:
It's taken me over a month to get my skimmer tuned. Doesn't help that I don't have any bioload yet. I found that tiny little adjustments need to be spaced really far apart. I made the error of over adjusting too frequently

Yeah, when I first installed the skimmer I was making adjustments and expecting results too soon. Would go from skimming nothing to having the cover floating and overflowing back into sump. "Nothing happens fast... " I know, I know. I got that now! lol

SurfLife · May 18, 2018

Halal Hotdog said:
Yes wet skimming can lower your salinity if your ATO is replacing the water with pure RO/DI water. Also typically there is no harm in turning off your skimmer for one week. If you suspect there maybe a leak or other issue, then turn off the skimmer and monitor your salinity for any drop. Salt creep can affect salinity, but typically is nothing significant unless you have mounds of it building up in a very short period of time.

I am still going with the wet skimming and ATO. Zero signs of any kind of leak and the creep is minimal, never mounds.

Bayareareefer18 · May 18, 2018

That's what happened to me I was pulling so much wrt skimmate my salinity dropped to around 32ppt. Fortunately I have no livestock yet so I just had a couple cups of salt to the tank and brought it right back to range.
I also just got my bottle of accurasea in the mail and found that calibrating refractometer with RO definitely was not accurate

Randy Holmes-Farley · May 18, 2018

The salinity of skimmate is very close to tank water salinity, so removing 1% of the tank volume in skimmate (say, 2.2 gallons from 220 gallons) and replacing with fresh water will decrease salinity by 1%, or from a sg of 1.02700 to 1.02673.

SurfLife · May 18, 2018

Randy Holmes-Farley said:
The salinity of skimmate is very close to tank water salinity, so removing 1% of the tank volume in skimmate (say, 2.2 gallons from 220 gallons) and replacing with fresh water will decrease salinity by 1%, or from a sg of 1.02700 to 1.02673.

Thank you Randy. Although I lose around 1-2 gallons a day by evaporation(I run de-humidifiers in basement where sump is), I know I am not pulling 2 gallons of skimmate per week. I have another possible cause to this but am not going to bring that up until I have a bit more time to verify. I will of course be returning with an update after a few weeks of daily monitoring.
Either way, still learned something I did not know prior