Introduction: Cheap Timer Based Auto Top-Off System

About: I like building things that are cheaper then you can find in stores and can modify to suit your needs. Let's face it companies build for the masses, I build for me! Anything IoT, Reef Keeping and Aquaponics a…

If you have an aquarium, especially a reef tank, you are familiar with the water evaporation being a problem. There are a lot of Auto Top-Off (ATO) solutions out there (JBJ, eshopps and Tunze) but the main problem is they are very expensive, between 150$ - 300$, depending in the manufacturer and the sensors will fail, it's not an if, it's when. Depending on warranty and reason for failure, it could be very expensive to replace the sensor. Most manufacturer's do make the ATO fail in the off mode, but make sure you check before purchasing.

There are also some homemade one's that require you to splice an extension cord and attach a cheap float switch (see picture) to the extension cord. Some examples introduce a relay to protect the float switch, which is better but as it protects the float switch from overloading, but you are still relying on a cheap float switch. Even if you get a better float switch they still have the same problem. the sensors will fail, it's not an if, it's when.

The other problem with both retail and DIY versions I see, are that they rely on sensors to trigger the pump, The sensors are a lot more sensitive then I believe is necessary. Using a sensor will trigger the pump many times during a day depending on the rate of evaporation which I don't believe is necessary and will likely shorten the life of your pump.

With the above options not sitting well with me, I decided to build my own.

Step 1: What You Need!

Here is what you will need to construct your project/

  • Tom's Aqua Lifter - 20$ or similar
  • a way to circulate the water in the bucket (a cheap wave maker is more then enough) 8$
  • Timer (Use a digital timer, not a mechanical timer) 10 - 20$
  • 5 Gallon Bucket and top (I used an old salt bucket)
  • Drill and hole saw (You can use a knife instead)
  • Something to weigh the tubing that goes into your bucket, a small bulk head works great
  • Tubing for your pump, length depends on how you install it.
Keep in mind that Tom's aqua lifter can only push water about 20" -25", your pump may have more or less capability. Also depending on the flow you may need a flow limiter, as you want a very low flow.

Step 2: Putting It All Together!

I chose this setup because I believe a timer is a better solution then a sensor. You can easily calculate the amount of evaporation over a couple of days to tune your timer or add a flow limiter if needed. I believe that this will extend the life of your pump and only have two parts that would need to be replaced, both of which are pretty darn cheap.

NOTE: Salt water tanks always use fresh water for ATO, water evaporates, salt does not.

It's a pretty easy set up and shouldn't take more then 20 min.

  1. Find a suitable place for your bucket and pump (make sure you have a drip loop for the pump)
  2. Measure your tubing lengths and cut or purchase accordingly.
  3. Drill or cut a small hole in the bucket cover to allow the power cord for the power head to pass through.
  4. Fill the bucket with the type of water your tank needs
  5. Place the power head into the bucket and plug it in.
  6. Place the input tube into the bucket, I find it better to weigh the tube down a bit, I used a small bulkhead
  7. Attach the top to the bucket, with the tube and power cord through the hole.
  8. Place the output tube into your sump or directly into your tank.

That's it your done.

Step 3: Let Er Rip!

A few final notes and suggestions.

The reason I used a digital timer instead of a mechanical timer is that a mechanical timer can fail in the on position. They also have buttons or pegs that can come lose or get stuck, none of this this would be good. A digital timer should have a battery backup, so if the power goes out your settings aren't lost and they generally fail and start in the off position.

Some plastic buckets can leech chemicals into the water, so be careful. There is much debate on what type of plastics are good for aquariums. Generally accepted plastics for aquarium use are #2 HDPE (high density polyethylene), #4 LDPE (low density polyethylene), and #5 PP (polypropylene), These labels are usually on the bottom of containers. You don't have to use a plastic container, you can get a small aquarium or other type of container

You also want to make sure that you aren't going to overflow your tank. The size of top up container should not be more then 5 gallons. This limits the risk if something goes wrong, at worst you put 5 gallons in your tank when it's at full capacity, not a huge mess compared to say a 15 or 20 gallon container.

I would suggest starting with your timer turned on for 5 minutes a day and set the flow to 1/2 rate, if using Tom's water lifter, if you are using a different pump adjust accordingly. Evaporation rate's don't change that much, it may slightly change once or twice a year during winter and summer. So just keep an eye on your tank for the first couple of days and make adjustments. Ideally you would like the pump to run for 10 minutes, twice a day.