Water change disaster. What did I do?

[Johnny C]

I have a 265 gallon display with what I figure out to be about a 15 gallon sump. I mixed up 33 gallons of water my salts matched up perfectly 35.3 in the aquarium 35.3 in the trash can. I tested other water just to make sure my Hannah salinity checker was working properly. My temperature was very close but not exactly 78 in the tank and 77 in the trash can. I slowly changed out the water. Just over 3 hours this took me. Not even thinking salinity would change at all. Then apex alerts me my salinity plummeted so now I’m playing catch up and trying to get my salinity levels back up. Any ideas what could have happened? What did I do wrong? How can I avoid this from happening again? I’m still way low my levels are now at 31.5 and I am introducing salt back in the tank every couple of hours. Is this the best or correct way to get my levels back up?

 

[SR Reefing]

Apex salinity prob is not the most accurate. When did u last calibrate it?
Did temperature of ur tank drop as well? (Notice the salinity prob reading low when temperature is lowered. )

U should really test ur salinity with a more reliable source.

 

[reefwiser]

Have you check it with a refractometer?
I wouldn’t relies on a salinity probe. As they are notoriously bad for reading properly.

 

[Reefer1978]

Do you have an ATO and did you remember to turn it off?

 

[Thaxxx]

If you have any other salinity devices to measure to your salinity, check it. that would be my first advice I wouldn't count on Apex to be consistent with salinity readings.
Then if it's still low, mix salt with current water in batches in container and add slow.

 

[Gablami]

Do you have an ATO and did you remember to turn it off?

This. If you changed water over 3 hours and did not turn off ATO, it can run the whole time and drop salinity.

 

[Timfish]

As a check against salinity testers and refractometers I always measure the amount of salt to get the correct salinity for the volume of fresh water I'm working with. This has alerted me several times when test equipment has had calibration drift.

 

[Reefer1978]

I have serious doubts this is a calculation / measurement mistake. Would take about 20 gallons of fresh water (if my math is correct, someone please double check) to bring 265 gallons from 35ppm to 32ppm. My money is still on ATO. Even with a slow water change, water drops below trigger, some fresh water is dumped in by the ATO. Over 3 hour span this would add up.

 

[newbie2014]

Would an ATO run for 3 hours non-stop? That should be the next thing to fix.

 

[Reefer1978]

Would an ATO run for 3 hours non-stop? That should be the next thing to fix.

ATO can run as long as you let it, especially if it turns on/off over 3 hours.

 

[Flippers4pups]

As others have stated, I would not trust the apex probe. Use a trusted refractometer that’s been calibrated with calibration fluid. Test your water before doing anything else.

 

[EMeyer]

Would an ATO run for 3 hours non-stop? That should be the next thing to fix.

Agreed, I run all my ATOs on a timer so they cant runaway and dump the whole bucket. They only turn on for a few minutes once an hour. Its a pretty easy safety feature.

 

[newbie2014]

Agreed, I run all my ATOs on a timer so they cant runaway and dump the whole bucket. They only turn on for a few minutes once an hour. Its a pretty easy safety feature.

Exactly. Why would you setup an ATO without a fail-safe (to run continuously)? As I understand my Tunze 3155 only runs continuously for 10min then shuts off. Maybe there’s a way to override it. I dunno I never bother to find out.
I also concur with others; double check it with a refractometer to confirm.

 

[Cell]

OP update? Hopefully they aren't dumping loads of salt into the tank before rechecking.

 

[Reefer1978]

Exactly. Why would you setup an ATO without a fail-safe (to run continuously)? As I understand my Tunze 3155 only runs continuously for 10min then shuts off. Maybe there’s a way to override it. I dunno I never bother to find out.
I also concur with others; double check it with a refractometer to confirm.

Your tunze is exactly the issue. It runs continuously for 10 minutes in a single go. But, if you are working on a slow water change like the OP over 3 hours, you are turning it on / off multiple times, thus resetting the 10 minute trigger.

 

[newbie2014]

Your tunze is exactly the issue. It runs continuously for 10 minutes in a single go. But, if you are working on a slow water change like the OP over 3 hours, you are turning it on / off multiple times, thus resetting the 10 minute trigger.

Actually NO. It completely shuts off with red led blinking. It won’t restart until I reset it, unplug/plug the power cord.

 

[Reefer1978]

Actually NO. It completely shuts off with red led blinking. It won’t restart until I reset it, unplug/plug the power cord.

Not true, I have 2 of them. It shuts off only if it runs for 10 minutes. But you can keep running it in 5 minute intervals many times. It's a very simple program that runs it.

 

[rwreef]

How do you make a 15g sump work on a 265g tank?

 

[Cabinetman]

The salinity probe is probably whacked. If I walk by my tank the wrong way it goes crazy. Sometimes it goes way high. Sometimes way low. I don’t even pay attention to it anymore. To unreliable

 

[Johnny C]

Apex salinity prob is not the most accurate. When did u last calibrate it?
Did temperature of ur tank drop as well? (Notice the salinity prob reading low when temperature is lowered. )

U should really test ur salinity with a more reliable source.

Apex is about a month old and that’s when I calibrated it last but I use a Hannah salinity checker and I calibrated it right before my water change and both read relatively close