ATO with no float switch

cope413 · Mar 9, 2015

I've read hundreds of posts about various ATO systems and I can't recall any of them that used the Salinity/Conductivity measurement in the tank over a float switch or valve.

I'm assuming I'm missing something because that seems to be a much more accurate way to do it.

I've only recently gotten an apex, so it hasn't been an option for me until now.

Is there a reason I shouldn't write a program to kick on my aqualifter pump when my salinity drops below a certain point?

Obviously it would need to turn on for a set period and then have a defer statement to allow the water to circulate and the probe to adjust to the new reading, but it sure seems to be a much better option than a couple of float switches...

-Logzor · Mar 9, 2015

In my opinion, a float switch or sensor is the best method. Regardless of salinity, water level must be maintained. I think the issue is the accuracy and reliability of salinity probes and the issue of other factors beside evaporation that impact salinity. For instance, dosing two-part can increase salinity over time, then your probe would be confused, adding too much water and flooding your system! In actuality, you need to replace saltwater with RO/DI in this scenario.

In theory it could work but I can envision more than one nightmare scenario.

cope413 · Mar 9, 2015

I would need to lose a lot of water relative to my system size (10-12g on a 40/20g) for my system to fail. Alarms and other things would certainly be triggered if it ever reached that level, so the ATO isn't meant to maintain water level. It's meant to maintain stable salinity.

This is the past week. Each little dip was when I added RODI.

Not sure what you mean by "my probe would be confused". If my probe is calibrated, then I can trust it. If I can't, there's not much point to having it in the first place, right? I dose 2 part, but I dose the same amount every hour.

It looks like my salinity rises ~.8ppt every 24 hours if I don't add any fresh water.
That makes sense because I have approximately 55g total water volume, and I go through about 5-6g/week in my ATO.

So why would I not want to make a program that kicks on my ATO pump when conductivity/salinity hits a certain level, have it run for X amount of time, then have a waiting period (say 30 minutes), and then turn back on again if the Cond. doesn't lower enough, run for X amount of time, wait, etc...

Up2no6ood · Mar 10, 2015

I would use the salinity probe in conjunction with a float. Have the float control the ato and salinity as a safety shutoff. The problem I see with just using the probe is there is no backup. If the probe fails, or gives a false reading there is nothing to fall back on. I however love the idea of using a salinity probe as a alarm. I often take water out of the tank when I trade frags or water samples. Last week I forgot to replace what I took out with saltwater and my ato made up the difference and dropped the salinity. Nothing bad happened but it would have been nice to have a probe that would shut off the ato if salinity falls below a certian threshold.

-Logzor · Mar 10, 2015

Up2no6ood said:
I would use the salinity probe in conjunction with a float. Have the float control the ato and salinity as a safety shutoff. The problem I see with just using the probe is there is no backup. If the probe fails, or gives a false reading there is nothing to fall back on. I however love the idea of using a salinity probe as a alarm. I often take water out of the tank when I trade frags or water samples. Last week I forgot to replace what I took out with saltwater and my ato made up the difference and dropped the salinity. Nothing bad happened but it would have been nive to have a probe that would shut off the ato if salinity falls below a certian threshold.

I agree with this strategy.

Typically the ATO is needed to keep water level consistent so that return pumps don't dry up and skimmer performance is maintained. ATO's typically have a failsafe, I would not trust the probe alone. Using the probe as an alarm can alert you when you need to make manual adjustments to salinity.

My point about two-part is that, over a long period of time salinity increases because NaCl is not consumed by corals from two-part dosing. Therefore your probe would be telling the system it needs more RO/DI when in reality you need to remove water and replace it with RO/DI. Over time it would increase the amount of water in your system and eventually overflow.

cope413 · Mar 10, 2015

Up2no6ood said:
I would use the salinity probe in conjunction with a float. Have the float control the ato and salinity as a safety shutoff. The problem I see with just using the probe is there is no backup. If the probe fails, or gives a false reading there is nothing to fall back on. I however love the idea of using a salinity probe as a alarm. I often take water out of the tank when I trade frags or water samples. Last week I forgot to replace what I took out with saltwater and my ato made up the difference and dropped the salinity. Nothing bad happened but it would have been nice to have a probe that would shut off the ato if salinity falls below a certian threshold.

Great point and idea. I think this is the way I'll do it.

-Logzor said:
My point about two-part is that, over a long period of time salinity increases because NaCl is not consumed by corals from two-part dosing. Therefore your probe would be telling the system it needs more RO/DI when in reality you need to remove water and replace it with RO/DI. Over time it would increase the amount of water in your system and eventually overflow.

After a disaster in college, when money was tight, and I didn't possess much common sense, I learned my lesson about not having a system where overflowing is possible.

Return pump could fail and not overflow my sump, even with a simultaneous fail of ATO. It's really shocking how much damage just 15 gallons of water can do...

Robert_ellis · Mar 11, 2015

-Logzor said:
I agree with this strategy.

Typically the ATO is needed to keep water level consistent so that return pumps don't dry up and skimmer performance is maintained. ATO's typically have a failsafe, I would not trust the probe alone. Using the probe as an alarm can alert you when you need to make manual adjustments to salinity.

My point about two-part is that, over a long period of time salinity increases because NaCl is not consumed by corals from two-part dosing. Therefore your probe would be telling the system it needs more RO/DI when in reality you need to remove water and replace it with RO/DI. Over time it would increase the amount of water in your system and eventually overflow.

I noticed the salinity rise after a few months of 2 part. It is true. Mine stays in check by the water I take out from frags and replace with ro. But I have a 200 with sump so changes are minimal. Small systems it would be more hazardous.