SG variability even with ATO in place

[old_turkey]

hi there,

so I have a small ATO in place for my tank but I'm still noticing the SG rising in my tank (over the span of a month or two) from 1.028 up to 1.03 or slightly above which I assume means the salinity has gone up in my 13.5 tank.  the initial way I tell is when my GSP just doesn't open up for a day or two (when I notice that I tend to measure SG).  I wind up addressing it by just suctioning out some water and letting the ATO kick in.  I also notice some salt buildup on the top edge of the tank over time as well.

so... two questions:

1) what do you do with the salt buildup on the glass?  shove it back into the water?  (that feels like it would raise up the SG further)  just wipe it away when I see it?

2) is this typical?  (the swings in SG)  as its over the span of a couple months, should I be concerned?   my ATO is a 5 gallon tank and I refill it maybe every 2-3 months.

 

bonus question: is this implying I should be doing more maintenance in the tank or should I be checking for specific things?

[ReefGoat]

IMO your problem is that your tank only needs 5 gallons of fresh top off every 2-3 months. That doesn't sound right from my experience which doesn't mean much. Does your tank have a lid? When I had an IM10. My ATO rate was about 5 gallons every two weeks. On my 45G It's about 7 gallons a week. My salinity hasn't budged one bit since the tank was set up. Which is approaching 3 months. Are you sure you're not spiking the salinity on accident just a little bit when you do water changes? 

[paulsz]

1 hour ago, old_turkey said:

  my ATO is a 5 gallon tank and I refill it maybe every 2-3 months.

 

 

That does sound like a very little amount of refilling. 

 

How do you check your salinity? Refractometer or Hydrometer?

 

Like ReefGoat mentioned, are you sure that when you do your water changes, you are going back to the exact same water level that you were before? 

 

Is there any way that salt could be getting into your ato reservoir (did you ever accidentally put mixed saltwater instead of freshwater in there without realizing)?

 

 

[old_turkey]

hmm.  it is an open mesh top (its a Fluval 13.5) that sits in my home office and I keep the house between 68-80 most of the year.  I'm not sure why I'm not experiencing more evaporation.  My freshwater tanks in another part of the house I'm topping off every week manually (maybe 1 gallon in a 20 gallon and .5 gallon in a 5 gallon each week).

The tank itself is approaching 1 year old and I've had the ATO in place for about 6 months or so I think.

I've only refilled the ATO completely once and its now down to half full (about to refill and get another 5 gallons of RODI this weekend)

 

I actually have not been doing water changes the last few months (it sounds like I need to step up on this), although I plan to this weekend as well since I noticed the pump was slowing down so I was going to replace the pump and suction the back chamber while I was doing this.   When I had been doing water changes, I was doing 1.5-2 gallons and refilling up to the dotted marks on the top of the Fluval tank, but things seemed fairly stable (no pests/algae breakouts) other than an early bubble algae spate that seems to have gone away so I stopped to see what impact that may have.

 

I am checking using a refractometer that does seem accurate (I tested both the RODI and tank water).  I don't think I'm mixing salt and RODI water when I did do water changes previously (I have a giant blue sticker on the RODI container in fear of mixing them).

 

[paulsz]

With a refractometer, you must be calibrating it with RODI water (it should be calibrated to 1.0 with RODI before testing the saltwater). I assume that you are doing that every time you test it? Because the refractometer could go out of calibration after a while. 

 

As for the ATO, is the switch getting lower? Where is it located and how is it attached to the tank (magnet, suction cup, etc?)

 

A side note: you may want to lower your salinity to 1.026. Overall, i think that's where most people keep it.

[RayWhisperer]

No. A refractometer needs to be calibrated with a calibration solution of 35ppt. Even though most refractometers directions say to use RODI, you shouldn’t. https://www.marinedepot.com/Brightwell_Aquatics_Refractometer_Calibration_Standard_60ml_Calibration_Fluid_Reagent-Brightwell_Aquatics-BW01907-FITECL-vi.html?utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=BW01907&gclid=EAIaIQobChMIssXJmLeO3wIViEBpCh0zzA9dEAQYASABEgIjNfD_BwE

always calibrate equipment to what you are trying to match.

 

As to the OP’s questions. That amount of rise is pretty much nothing over a 2 to 3 month period. I have a few guesses, but that’s really all they are at this point. First, are you sure that the ATO is refilling to the same point? Now, on a larger system that 1/16” difference won’t mean squat.  But on a small enough volume of water, it could possibly account for the difference.

 

Second, salt creep (what you described as salt buildup) could be falling back into the tank. A few guesses as to how this could be happening. First, some falls in while wiping it off. Second, condensation could dissolve the salt and drop it back in. However, both of these scenarios account for salt creep on a system that hasn’t had a water change. That would mean relatively constant salinity, or a slight drop due to the removal of salt creep.

 

The most likely scenario, imo, is the way you are measuring your salinity. As mentioned before, a refractometer is far more accurate than a swing arm hydrometer. That alone could account for the discrepancy. Then there is proper calibration. That could easily cause a false read, as well. Not to mention temperature. Now, most refractometers are temperature corrected. However, they still need to be close to 70 ish degrees. Too far off, and things start to change. 

 

I have  some suggestions for your tank, as well. You mentioned your pump was slowing down. Now, lack of water movement could account for the relatively low evaporation. If the pump is adequate for the size of your system, there is no need to replace it. Just a simple disassembly, cleaning, and reinstallation of the pump and return tubes will significantly increase the volume of water your pump is pushing. However, if the pump is too small to begin with, an upgrade will probably be in order. Either of those alone will increase your evaporation rate. 

 

 

 

 

[old_turkey]

thank you for the comments.  

I will look into calibration solution.  My method previously was to check that the water in the ATO was at 1.0 and then measure from the tank after.

I was assuming that with the salt creep the SG should have gone down as mentioned so I was curious why it was going up.  

 

The ATO is in the back chamber of the tank above where the pump is.  The sensor is an LED help up by a magnet and is roughly 1" from the top of the tank.  I do not believe its moved at all, but that's something I did not think about and can track.  

I have a second pump and have swapped them out in the past.  I do clean the removed pump after pulling it from the tank.  Sounds like water change and use that water to rinse out the pump is my plan for the weekend.

[Clown79]

That does seem like a very small amount of water topping up. Odd for sure.

 

I manually top up 1 time a day.

 

My 25g uses a full juice jug every day

My 5g uses less than a cup

My 10g use 1.5 cups

 

So it seems odd that an open top tank with an ato is using so little.

 

Definitely calibrate with 35ppt solution. I found using distilled was inaccurate. Mine was off a bit while using the distilled water that came with my refractometer.

 

 

[old_turkey]

well I have swapped out pumps (and noticed a change in water level in the main tank area).  I'm guessing evaporation will go back up.  

also with the water changes, I guess I'll need to start placing a heater in the water containers for a while to get the temperature up to near tank levels, but I've also managed to lower the SG overall to closer to 1.026.  I assume people do not put a water heater in the ATO container since it should in theory be a small amount being added at any given time?

 

 

[paulsz]

12 hours ago, old_turkey said:

 I assume people do not put a water heater in the ATO container since it should in theory be a small amount being added at any given time?

 

 

Yes, that's right. No need for a heater in the ATO

[specore]

On 12/7/2018 at 2:04 PM, paulsz said:

With a refractometer, you must be calibrating it with RODI water (it should be calibrated to 1.0 with RODI before testing the saltwater). I assume that you are doing that every time you test it? Because the refractometer could go out of calibration after a while. 

 

As for the ATO, is the switch getting lower? Where is it located and how is it attached to the tank (magnet, suction cup, etc?)

 

A side note: you may want to lower your salinity to 1.026. Overall, i think that's where most people keep it.

As @RayWhisperer pointed out, this is dead wrong.  Refractometers should ALWAYS be calibrated with 35ppt solution and using RO/DI can result in a very inaccurate reading. 

[paulsz]

26 minutes ago, specore said:

As @RayWhisperer pointed out, this is dead wrong.  Refractometers should ALWAYS be calibrated with 35ppt solution and using RO/DI can result in a very inaccurate reading. 

someone should tell the refractometer suppliers to change their instructions.

[specore]

1 hour ago, paulsz said:

someone should tell the refractometer suppliers to change their instructions.

If you were trying to measure sg closer to 1.0 then to/di would be better.  So in some applications that is the case.  I have seen cases on these forums of things going horribly wrong because a refractometer calibrated to 1.0 was not reading accurately in the 1.025 range, which is no big deal in fowlr setups.  

[Clown79]

3 hours ago, specore said:

If you were trying to measure sg closer to 1.0 then to/di would be better.  So in some applications that is the case.  I have seen cases on these forums of things going horribly wrong because a refractometer calibrated to 1.0 was not reading accurately in the 1.025 range, which is no big deal in fowlr setups.  

Exactly.

Refractometers are not just used for salt water tanks so depending on its use will depends on its calibration.

 

 

[paulsz]

41 minutes ago, Clown79 said:

Exactly.

Refractometers are not just used for salt water tanks so depending on its use will depends on its calibration.

 

 

But when it's made for aquariums (Red Sea for example, only because that's the one I have) and it states to calibrate via RO/DI, is that not sufficient? Just asking because if I had not come onto forums, I wouldn't have known to use calibration solution. And I'm guessing not everyone who has it reads these forums.

[Clown79]

Mine came with a distilled solution.

I then purchased calibration fluid at the recommendation of others.

 

I'm glad I did. Mine was off. 

 

I prefer to calibrate it with 35ppt solution.

[MrObscura]

My nuvo 10 evaporates between 1-2 gallons a week, enough per day that my salinity would fluctuate with just 1 manual top off per day. 

[specore]

1 hour ago, paulsz said:

But when it's made for aquariums (Red Sea for example, only because that's the one I have) and it states to calibrate via RO/DI, is that not sufficient? Just asking because if I had not come onto forums, I wouldn't have known to use calibration solution. And I'm guessing not everyone who has it reads these forums.

Not sure why they would instruct that, maybe they are just private labeling a laboratory refractometer and diidn't bother to update the directions with aquarists in mind?   Main thing is you want to know when it says 35 ppt that your water is actually 35 ppt.  Calibrating with RO/DI only means you are sure 1.0 sg really means 1.0 sg, but that doesn't necessarily mean the same refractometer is reading correctly at other values than 1.0

[MrObscura]

Every sality tester I've seen had directions that say to calibrate with rodi. Theoretically it probably would work, but since we want to test water with higher salinity it makes sense to calibrate it there for the best accuracy. 

[docshipwreck]

+1 on the calibration solution. I understand where you're at with the directions. I did that to zero mine out then went with the solution. I read quite a few articles about the salinity calibrations at the higher concentrations. As far as water changes I do my very best to take out and put back the same amount, i.e a 5 gal bucket. I know then from a volume standpoint my ATO shouldn't be off even with fresh filtration media I'm at the level I need to be, 

 

I have a hydor ATO, not my first choice but I couldn't pass up the deal I got it at. Its definitely trick to get dialed in, I also have not been able to measure the swing before I kicks on. I have a biocube 14. My ATO reservoir designed to hold a drink for dispensing in the fridge, Im not sure off the top of my head of how much water it held but its at least one gallon, I think even in summer with AC on in my apartment its gone 5-7 days before I should refill. 

 

If you think something is weird draw on your tank in marker or grease pencil and date it. 

[johnmaloney]

On 12/7/2018 at 11:56 AM, old_turkey said:

hi there,

so I have a small ATO in place for my tank but I'm still noticing the SG rising in my tank (over the span of a month or two) from 1.028 up to 1.03 or slightly above which I assume means the salinity has gone up in my 13.5 tank.  the initial way I tell is when my GSP just doesn't open up for a day or two (when I notice that I tend to measure SG).  I wind up addressing it by just suctioning out some water and letting the ATO kick in.  I also notice some salt buildup on the top edge of the tank over time as well.

so... two questions:

1) what do you do with the salt buildup on the glass?  shove it back into the water?  (that feels like it would raise up the SG further)  just wipe it away when I see it?

2) is this typical?  (the swings in SG)  as its over the span of a couple months, should I be concerned?   my ATO is a 5 gallon tank and I refill it maybe every 2-3 months.

 

bonus question: is this implying I should be doing more maintenance in the tank or should I be checking for specific things?

Add anything like magnesium that could be adding to specific gravity?