Looking for suggestions on Sumpless ATO setups

So here is my question…. Does the water surface agitation from the powerheads and filters in your tanks cause issues with the ATO ever filling too much to cause fluctuations in your salinity??
No, It has no effect on my tank
 
Right I understand that but what but I don't understand is why an ATO for a system without a sump is any different than an ATO for a system with a sump. An ATO is an ATO regardless, or so I thought until now. I've never heard of a special ATO needed for a system with no sump but I don't get out much 🤪
IMO...Marketing....the same as a "Reef Ready Aquarium" versus an aquarium with an overflow.....
 
Can someone please explain the difference between a sumpless ATO and a regular one? I'm just not getting it and never knew there was such a thing.

I've ran this one in a sump and now in the tank and I've done the same with others
PXL_20250808_012216429.jpg
A system with no sump is Just a tank and hang on filter and the sensor has to be in the tank.

Only issue would be that heavy surface agitation may effect the sensor.

Also I run 4 of the new Tunze units and the sensor does not like stray light so I dont think it will work in tank unless you can over it from the light.
I had to do this on my nano. The light causes the sensor to overfill.
I blocked the light per Roger from Tunze and no issues.
 
A system with no sump is Just a tank and hang on filter and the sensor has to be in the tank.

Only issue would be that heavy surface agitation may effect the sensor.

Also I run 4 of the new Tunze units and the sensor does not like stray light so I dont think it will work in tank unless you can over it from the light.
I had to do this on my nano. The light causes the sensor to overfill.
I blocked the light per Roger from Tunze and no issues.
Ya i get the sump no sump just had never heard of a ATO specific to one or the other.
I like my $50 Amazon ATO over my tunze. The tunze is sensitive to light as you mention and it seems to need cleaned more often. The sensor on the cheap unit shown above is sitting in a 40g breeder under a photon with a gyre in the tank and it doesn't skip a beat.
I still prefer my JBJ units with float switches instead of the new fangled optical sensors. I find it interesting that my tunze has a float switch as the failsafe.
 
Ya i get the sump no sump just had never heard of a ATO specific to one or the other.
I like my $50 Amazon ATO over my tunze. The tunze is sensitive to light as you mention and it seems to need cleaned more often. The sensor on the cheap unit shown above is sitting in a 40g breeder under a photon with a gyre in the tank and it doesn't skip a beat.
I still prefer my JBJ units with float switches instead of the new fangled optical sensors. I find it interesting that my tunze has a float switch as the failsafe.
No float switch on their new 3154 units it is all.sensor driven
I have 4 that have never been cleaned in over a year. Thanks for the reminder. I am going to look at them today.
I used both of the old units with floats. A few times snails would cause the unit to not work proprlerly.
I would not want a float switch in my tank for many reasons and snails are only one of them.
The new Tunze nano I run on my 15 is considerably better than the old one, imo.
 
So here is my question…. Does the water surface agitation from the powerheads and filters in your tanks cause issues with the ATO ever filling too much to cause fluctuations in your salinity?? Because for instance I know when it’s in your sump, the water in your sump is relatively calm and stays at the same water level because you don’t really have much surface agitation as you would inside your main tank from powerheads and filters and what not if you get what I’m saying
I have my sensors tucked away in the back corners of the tank behind other equipment which protects them a bit, including from surface agitation. That said even with a lot of surface agitation it's not a big deal (in my opinion), just place your sensor level at the trough of the "waves".
 
No float switch on their new 3154 units it is all.sensor driven
I have 4 that have never been cleaned in over a year. Thanks for the reminder. I am going to look at them today.
I used both of the old units with floats. A few times snails would cause the unit to not work proprlerly.
I would not want a float switch in my tank for many reasons and snails are only one of them.
The new Tunze nano I run on my 15 is considerably better than the old one, imo.

Not knocking tunze, they're a great company with awesome products.

They both work but given a choice I'm going mechanical over a sensor, it's just how I'm wired pun intended. The float switch I posted on page one was in a sump for 6 years and never cleaned. It's now doing duty in the rear chamber of my IM20
I know everything is going to fail but I have JBJ float switches that have been in use for 9 years. Its too bad no one I know of makes an ATO unit with only float switches these days.

PXL_20250808_161435045.jpg
 
Not knocking tunze, they're a great company with awesome products.

They both work but given a choice I'm going mechanical over a sensor, it's just how I'm wired pun intended. The float switch I posted on page one was in a sump for 6 years and never cleaned. It's now doing duty in the rear chamber of my IM20
I know everything is going to fail but I have JBJ float switches that have been in use for 9 years. Its too bad no one I know of makes an ATO unit with only float switches these days.

PXL_20250808_161435045.jpg
Love the JBJ ATOs I had (still have one in my garage) just wish i had thought of the stocking trick cause a snail stuck mine on and nearly flooded my sump.
 
Not knocking tunze, they're a great company with awesome products.

They both work but given a choice I'm going mechanical over a sensor, it's just how I'm wired pun intended. The float switch I posted on page one was in a sump for 6 years and never cleaned. It's now doing duty in the rear chamber of my IM20
I know everything is going to fail but I have JBJ float switches that have been in use for 9 years. Its too bad no one I know of makes an ATO unit with only float switches these days.

PXL_20250808_161435045.jpg
It's interesting how we reefer stick with one product over others.
Im no different as I have ran Tunze forever. Us old reefer stick with what works.
 
The ATO in my display tank drops too low before my sensor kicks on I’m hoping this sumpless one I just ordered prevents that and keeps it more stable
 

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