Best deal and quality ATO system for a 40g reef?


New member
Hey guys, I'm setting up a new reef tank and I'm looking into getting an ATO since I want to have an open top. I've done just a teeny bit of research and found that most ATOS are expensive and some of the super cheap ones I'm worried are bad quality... does anyone know a nicely priced ATO that will work for a 40 gallon? Thanks so much.


New member
I can only recommend the only one I've ever used. I have a 37 gallon with a sump. It has a DC pump and monitors high, mid, and low water levels. When it hits the low mark, it fills to the mid mark. I got this from Amazon for around 90. It works great and the only thing I did to make it work better (for me) was to mute the filling up alarm/buzzer. It's cool the first 2 times but gets old quickly. Anyway, most will point to another brand (tunze oscillator or...) because they have been around longer. Been using this since June. Good luck, and should ya pick it up, let me know. This is one category where I found everybody had an opinion and it was hard to not choose the $300 option, but overall I'm happy I didn't.



Convince'em or confuse'em
I've had the Tunze Osmolator on my 115 gal tank for over two years and it has worked perfectly.
I used the Aquahub DIY kit from BRS with a Neptune PMUP on my 30 gal for almost as long and it has worked perfectly.
Both take a little maintenance, periodically cleaning the optical eye and float switches. If either get built up with film or growth it will cause a problem, and has been the only reason I've ever had any trouble with either one. In both cases it prevented the pump from running, which is probably better than a pump not shutting off.
Haven't had to replace the Tunze pump yet (uh-oh, I just cursed it).
So, in my experience quality equipment is certainly important, but proper maintenance just as much. Pretty much goes for all equipment.


Super Best Friends!
Premium Member ATO. Get the dual float model. I bought mine used in 2008 and still use it. I bought a second one several years back that I've used off and on. No issues...just have to swish the floats in the sump water to clean them off from time to time.


Premium Member
I have used the Tunze Osmolator 3155 on my 120 for years and one on my new Nuvo 14. Very reliable. I have the JBJ ATO on my Nuvo 20 and it has worked well without any issues. I use a PMUP for this one.