Small DIY gravity fed ATO for my 2.5g pico reef

[DenverBC29]

We've probably all seen the dog water dish with the inverted 2 liter pepsi bottle. When the dog drinks the water, water level drops, allowing air into the bottle, allowing water to escape refilling the bowl. This simple build is using the same premise and I hope it is helpful to someone out there in reefland.

In one of my other threads:
http://reefcentral.com/forums/showthread.php?t=2048992

I build an AIO 2.5G reef tank for my office. To keep things as stable as possible, I've been topping off water morning and afternoon every day with small amounts of fresh RO/DI water. Well guess what? I don't work 7 days a week, so on Monday morning, the refugium/pump chamber is always about an inch low which can't be good for stability. After considering my options, I decided to build a small gravity fed ATO that will keep my refugium/pump chamber's water level consistently 2" below the glass cover.

Here we go...

I started by measuring my ideal water level to the surface of my glass top (that is scooted towards the front of my tank 1/4" leaving a small gap at the back of the tank for a small fan to blow and to leave room for the 2 tubes for this ATO) which came out to be 2". Knowing this, I had the only critical measurable in the design - my air tube needed to extend 2" out from the bottom of my ATO.

Selecting a good container was easy. I dug through my plethora of fish supplies and found a container that would sit nicely by my light and fan & hold enough water to last for a few days. It is a bottle of Kent Amonia Sponge.


Next, I inverted the container and set it where I wanted it located. I made 2 marks on the sides of the lid marking the beginning of my gap between the glass top and the edge of the tank. I then drew a line between them showing the small area where I would have to place my tubes. I marked 2 holes, one for air, and one for water.


I then found rigid tubing (i think 1/8") and cut it's length to be 2" on the outside of the lid and long enough on the inside to extend almost to the bottom of the bottle once the lid is installed. This tube will allow air to pass into the bottle once water drops below 2" from the top of the tank. When the water evaporates, it will allow air in, letting water out of the ATO until the air tube is under water again. The other tube is just standard airline tubing, but you could use rigid if so desired. This tube will allow water out of the ATO and into the pump section of my AIO. Length isn't super important, just make sure it will be long enough to be below the surface of the water. Appropriate holes were drilled in the lid and the lid liner was removed and drilled separately.


Once I test fitted the lines, it was time to prep it for paint (krylon fusion). I taped over the threads and placed a strip of paint on the side of the bottle to allow easy viewing of water level in the ATO.


The tube on top is the rigid line used for air. 2" sticking out to the left to control water level and enough sticking out on the right to go almost to the bottom of the bottle. The tube on the bottom is the airline tubing used for the water to flow through. This tube is only about 1/8" of an inch inside of the lid and extends about 4" from the lid. I installed the lid liner, then used superglue on both sides of the lid to glue/seal the tubes into place. It is important to have an airtight seal, so I hope the super glue and the lid seal works!


Fill the bottle with water, screw the lid on tight, and invert it for a simple gravity fed ATO!


More to come tomorrow when I take it to the office, fill it with water, and see if it actually works (and keeps my tank full on Saturday and Sunday).

Thanks for reading!

[Netofficer3710]

This is a cool concept!
I have been inspired to refine this idea and involve a pet water bottle (the kind with the ball and metal nozzle) and an acrylic bracket for the rim.

[twiggyb]

I'll have to try this if I can't keep the tank topped off. Even if I can I might do this anyway as that's one less chore when I get home

[Lalebeq]

tagging this thread interested to see how it turns out

[DenverBC29]

The ato didn't work well. The lid leaked air, so I super glued it shut. Then the flow was inconsistent, so I believe the airline needs to be bigger than the water line, not smaller. I'll build version 2.0 and post the results.