Aquarium Auto Top Off System Water Filler Compensator Blue, 1pcs

I have to say I was a skeptic! It before I spent $75+ on an ATO for a 15 g tank - I had to give this little gadget a go! It works exactly as it should and saves my nano reef from salinity spikes! Definitely recommend!

Simple and works great once set up.

Great product, works exactly as advertised. It's a very good price. Ended up buy 2.

I've finally gotten this ATO with a water bottle to work for about a day. I really like that's it's only based on gravity and natural vacuum. Pretty fantastic and hard for it to fail vs electric sensors. That being said, it took me awhile to get it to work, so here are a few tips: My experience is that this will Only work with Evian bottles. I tried Smartwater, Coke, and Fiji and all of them leaked, even with the included adapter, because the bottles have little vertical gaps in their threads that allow air to get in. This may be a change to those bottle's thread design so I can't blame this ATO. I also took one star off because the amount of tubing they provide is very short. I needed more tubing for my application but I found that PVC based clear airline tubing will Not work. It doesn't seal well enough against the water outlets and so it lets air in. My experience is that this ATO will only work with flexible, opaque silicone-based airline tubing. Hopefully someone else can take a shortcut from my learnings.

I've bought three of these at this point. They work exactly as advertised and are very good at keeping a constant water level in small tanks where evaporation is your primary nemesis. The tank in my pictures is 2.5 gallons and I was losing about a half inch of water to evaporation every day. To be honest, I'm a lazy fish keeper and i don't want to perform maintenance every day or even every other day. Weekly water changes are fine, but I don't want to take the time to top off manually, and I certainly don't want to pay for an electric ATO and have the wires and plumbing and everything in the way as well, so I really like this product.Not only does it do its job flawlessly, it is also a bulletproof design based on physics. It cannot fail catastrophically like an electric ATO because it doesn't use a solenoid and float valve, it only uses gravity. If the breather port is below the rim of the tank, it is impossible to have an overflow.Evian bottles still work fine (7/1/22) contrary to another user who I wish would edit their review. I use the Evian 1L bottle in all three applications I have, and I've never had a problem. I really hope this helps you choose this as an alternative to a typical ATO.If nothing else, use this as an electricity-free, disaster-proof way of topping up if you're gone for a weekend or something rather than risking a power outage or solenoid failure and being far away while your electric ATO pumps your entire reservoir of water on to your floor and kills your fish.10/10, I will absolutely buy more of these.

The media could not be loaded. Am I the only one that has trouble with this DA$& thing? It doesn't suck air in through the short air line. It sits there and siphons the whole bottle into my tank. Both hose release water and my bottle just has a vacuum on it and drains all the water out. I want this for a top off to leave for work but I can't get this dang thing to work properly. I turn the bottle over slow, it drains the bottle, I turn the bottle over fast, it drains the bottle. I pinch both hoses and turn it over, it drains the bottle. What am I doing wrong? I've watched every video on YouTube and not a single one addresses this problem.

So like everyone else, mine was leaking. I even used Smart water bottle (1.5L) and still it leaked. I saw a comment recommending to wrap the bottle thread with plumbers tape and that worked for me. So far it had not leaked and seems to be working.

Cheap and reliable, works great for my nano reef tank. I use empty “smart water” bottles for it. Highly recommend. Electrical ATOs often fail, but as long as we have gravity, this one won’t fail on you.