DIY Gravity Auto Top Off

[GSPClown94]

I haven't seen any posts on this site about the style of auto top off I used for my aquarium so here is how I made mine. This design uses a sealed container with two tubes, one for siphoning fresh water from the container into the aquarium and one for triggering the siphon to operate when the water level in the aquarium drops.

Items needed:
- 13/64 inch drill bit and drill
- 2 various lengths of 1/4 inch RO tubing
- Glass container
- Rubber stopper
- Vegetable oil

For my container I used a 4 liter bottle of Carlo Rosii sangria from Walmart, pro tip don't attempt to drink the entire bottle of sangria in one night. The size of the stopper will depend on the size of the opening on whatever container you use. For my application I used a #6 medium rubber stopper made by The Hillman Group which I found at Lowe's. I am not sure about the possibility of the rubber stopper leaching something into the water but because it wont be in contact with the water I am not too concerned about that.

Step 1
Start by drilling two holes in the stopper with the 13/64 inch drill bit. While drilling push the drill bit back and forth a few times from both sides to make sure the holes are smooth.

Step 2
Use a tooth pick to apply a small amount of vegetable oil to the inside of the holes in the rubber stopper, this will help with inserting the RO tubing in the next step.

Step 3
Shove the RO tubing through the holes in the rubber stopper in the direction of decreasing diameter. The tube circled in yellow only needs to be pushed through about in inch or two because this should not come in contact with the water inside the container. The tube circled in black should go all the way to the bottom of your container. If you are using kalkwasser in your auto top off then you can adjust this tube to be a few inches above the bottom to avoid sucking up the kalk slurry that settles to the bottom.

Step 4
Place the container somewhere above the aquarium and stick the other ends of the RO tubing into the aquarium. You will need to trim the RO tubing so that the one circled in yellow sits just below the surface, this can later be moved up or down to set the water level. Cut the tube circled in black so that it sits a few inches below the surface of the water. These tubes sitting in the aquarium need to be secured so that they are not accidentally moved.

Step 5
Fill your container with RODI water put the rubber stopper in making sure to get a tight seal.
Take the tube circled in yellow out of the aquarium and blow in it to start the siphon then put it back in the water, this is the tube that sets your water level. As the water level drops below this tube air is allowed to enter the container and freshwater is siphoned into the aquarium. Once the water level in the aquarium reaches this tube air will no longer enter the container and the siphon will be paused.


This style of auto top off can be made relatively cheaply and has no moving parts to wear out but there are some drawbacks. You need to be able to store your auto top off reservoir above the aquarium. Also if the container is not completely sealed and air is allowed to enter then the siphon will not stop until your container is empty. This also means that the tube that sets the water level in the aquarium must be properly secured so that it is not accidentally moved by either yourself or any tank inhabitants.

 

[Reef-junky]

Float valve is the easiest way to set this up. Then you don’t have to mess around with starting a siphon every time or worry about the seal. I would set it up like this. Any container would work and float valves are cheap. The reason most people probably don’t run this style set up is probably space.

 

[GSPClown94]

Float valve is the easiest way to set this up. Then you don’t have to mess around with starting a siphon every time or worry about the seal. I would set it up like this. Any container would work and float valves are cheap.

That’s nice but I wanted as little extra pieces of equipment in my nano as possible so two tubes going into the water looks a lot better than a float valve. Also blowing through a tube for 2 seconds to start the siphon isn’t much to mess around with. Ultimately it depends on what goals one has in mind for their aquarium for what route they take.

 

[cracker]

Used something similar for "years" worked just fine.

 

[Reef-junky]

I wouldn’t trust hoses working off a siphon like that. At the same time there’s no way I would put a float valve in the display though. A siphon can be broken and there’s no redundancy in your system to keep it working if that happens. To me it’s like the argument of drilling your tank vs having a HOB overflow. Do you want something that can fail or something that will work every time? For me it would be a pain to restart the siphon every time vs just filling a tank. Neat idea though and I like the fact that it’s out of the box thinking. I take it you have no sump to put stuff in then.

 

[GSPClown94]

I wouldn’t trust hoses working off a siphon like that. At the same time there’s no way I would put a float valve in the display though. A siphon can be broken and there’s no redundancy in your system to keep it working if that happens. To me it’s like the argument of drilling your tank vs having a HOB overflow. Do you want something that can fail or something that will work every time? For me it would be a pain to restart the siphon every time vs just filling a tank. Neat idea though and I like the fact that it’s out of the box thinking. I take it you have no sump to put stuff in then.

It would be rare for the siphon to break in this design, I am more concerned about maintaining a proper seal as to not let the siphon operate continuously. I'm not sure where you are getting the idea that float valves never fail, anything with moving parts is prone to failure at some point. Also you're right I don't have a sump.

 

[Ryane7]

https://www.reef2reef.com/threads/gravity-ato.347366/#post-4325656

 

[GSPClown94]

https://www.reef2reef.com/threads/gravity-ato.347366/#post-4325656

Thanks for sharing, I must have missed this when I was looking. Looks like you have been using this for a while, have you experienced any issues?

 

[Ryane7]

It has worked flawlessly except it is annoying to refill I have to do it every 5 days by running a hose thru top valve. I wish I had room for a larger tank

 

[Reef-junky]

It would be rare for the siphon to break in this design, I am more concerned about maintaining a proper seal as to not let the siphon operate continuously. I'm not sure where you are getting the idea that float valves never fail, anything with moving parts is prone to failure at some point. Also you're right I don't have a sump.

Never said float valves can’t fail that’s why they use more then one. What i’m sayIng is if the siphon fails your system has no back up. Nothing wrong with a gravity feed system. You could also use an upside down bottle that sit just below the surface.

 

[Reef-junky]

I am more concerned about maintaining a proper seal as to not let the siphon operate continuously.

When I say fail I mean any type of failure which would mean something like this. The designed posted in the link works from the bottom vs from the top like your set up. It also doesn’t rely on you making a good seal on something in order for it to function properly. By going from the top like that you have to start the siphon every time. It’s much safer to have something designed the other way. That’s the idea I was getting at with the picture. Your design has to fight gravity in order to work the problem is this type of system has proven unreliable on other things in the past. I’m not saying it will or will not fail but I would not trust it vs something like the link posted.

 

[GSPClown94]

Never said float valves can’t fail that’s why they use more then one. What i’m sayIng is if the siphon fails your system has no back up. Nothing wrong with a gravity feed system. You could also use an upside down bottle that sit just below the surface.

You're right you didn’t explicitly state that but it is what I interpreted from your previous posts. You provided your ideal design with a float valve and then asked if I want something that can fail or something that will work every time. It seemed obvious that you were referring to the design you provided. Also you later mentioned that you would use more than one float valve, however, there was only one in the diagram you provided.

 

[GSPClown94]

When I say fail I mean any type of failure which would mean something like this. The designed posted in the link works from the bottom vs from the top like your set up. It also doesn’t rely on you making a good seal on something in order for it to function properly. By going from the top like that you have to start the siphon every time. It’s much safer to have something designed the other way. That’s the idea I was getting at with the picture. Your design has to fight gravity in order to work the problem is this type of system has proven unreliable on other things in the past. I’m not saying it will or will not fail but I would not trust it vs something like the link posted.

The only point of failure you seemed to be mention was the siphon failing, it was definitely not clear you meant any kind of failure. Actually you are wrong, Ryane7’s design does rely on the container having a good seal. As with both his and my design any air leak will result in a continuous flow of freshwater into the aquarium. The “seals” in Ryane7’s design would be the bulkheads, the valves, the connections between the bulkheads and valves, and of course all of the pieces of acrylic siliconed together.

Also if the siphon on my design does fail I do not consider this to be a catastrophic failure, the only outcome would be that freshwater would not be topping off my aquarium and my salinity would increase due to evaporation. On the other hand if any of the seals are broken and air is allowed to enter the container then you would have a continuous flow of freshwater into the aquarium. The latter would cause harm much faster so in an effort to minimize the number of seals that could possibly be broken I chose to go with two tubes and a rubber stopper totaling 3 possible points air could enter the system excluding the ends of tubes. One design is not necessarily better than another, it all depends on one’s needs and goals for their aquarium. I just wanted to provide another way to do something.

 

[Reef-junky]

You're right you didn’t explicitly state that but it is what I interpreted from your previous posts. You provided your ideal design with a float valve and then asked if I want something that can fail or something that will work every time. It seemed obvious that you were referring to the design you provided. Also you later mentioned that you would use more than one float valve, however, there was only one in the diagram you provided.

I meant float switches not valves. The point is systems that are set up that way have redundancy. Float switches usually don’t. Nothing wrong with float switches but they can get stuck. Any good design has redundancy build in to it. Just relying on a siphon is to risky to me. I don’t want my ATO to be able to empty out into my tank or stop working and not catch it for a day or two but that’s just me.

 

[TinyChocobo]

Glad to see it works for you. It's not something I considered doing myself.

 

[Nick.B]

This is what I've been using on mine for about 5 years now. The ATO reservoir is hidden in a cabinet about 6 feet away from the tank. I could see why you wouldn't want a float valve in a nano though.

 

[telic]

Hello!
Brand new here, just signed up to reply here.
I'm looking to build exactly this, and at first I couldn't see how the siphon could be broken, or that there even is one.
But I think that's if the container is placed like in the picture?
I hadn't even thought about that, my idea was to hang the glass bottle upside down, which should make it pretty much fool-proof? Unless I'm missing something

 

[GSPClown94]

Hello!
Brand new here, just signed up to reply here.
I'm looking to build exactly this, and at first I couldn't see how the siphon could be broken, or that there even is one.
But I think that's if the container is placed like in the picture?
I hadn't even thought about that, my idea was to hang the glass bottle upside down, which should make it pretty much fool-proof? Unless I'm missing something

Welcome to R2R! Can you elaborate on your idea some more? Is it a completely different design or a modification of the one I originally posted?

 

[telic]

Welcome to R2R! Can you elaborate on your idea some more? Is it a completely different design or a modification of the one I originally posted?

Thank you! Been lingering for long
My original idea since years has been a glass bottle upside down, with 1 or 2 outlets made from stainless or glass, siliconed into the bottleneck, for hose to attach to.

I'm not sure how good a seal it would be with stainless though.


Now, looking at this self watering glass globe with a spike I have in a flowerpot, if I could find one that holds 1 liter or more, that'd be nice to use, and it looks very nice aswell
My tank's a fluval edge 23l (6ish gallons), so i don't need a whole lot of volume


With the bottle upside down, there's no siphon, and this should be fool-proof?

 

[GSPClown94]

Thank you! Been lingering for long
My original idea since years has been a glass bottle upside down, with 1 or 2 outlets made from stainless or glass, siliconed into the bottleneck, for hose to attach to.

I'm not sure how good a seal it would be with stainless though.


Now, looking at this self watering glass globe with a spike I have in a flowerpot, if I could find one that holds 1 liter or more, that'd be nice to use, and it looks very nice aswell
My tank's a fluval edge 23l (6ish gallons), so i don't need a whole lot of volume


With the bottle upside down, there's no siphon, and this should be fool-proof?

It sounds like you are trying to make something like this gravity-ato-icecap? You're right the upside down bottle doesn't use a siphon, it uses the air pressure in the ATO container to keep the water inside the container until the water level in the aquarium lowers and allows air to enter the container. I have no experience with this style ATO but some have mentioned some potential issues where the salt and freshwater end up mixing due to being in constant contact.
I wouldn't go as far as to say it's fool-proof, if the seal is broken and air gets into the ATO container then it will just dump all the fresh water into the aquarium. It's been a while since I started this thread but since then, I've moved on to having multiple smaller independent ATOs on my aquarium in case one does fail and dump all of the freshwater, the change in salinity won't be that catastrophic. Of course that comes with additional cost of having more equipment, space, and time needed to fill them up.