Saltwater Fish Tank Water Change System

Posted in Projects by Bill
17 Jan 2010

Not all my projects are robotic in nature. This one, a simple water change system for our 40 gallon saltwater tank, is one of those non-robotic projects. For those who are unfamiliar with fish tanks, about once a week you have to change out roughly 10% of the water. The way we have been doing water changes involved two trips to the toilet with a mob bucket, and a lot of mixing of water in the shower. I decided to build a better way.

The system consists of a valve manifold inline with the tank’s filtration system, a bilge pump, and a long hose to reach our kitchen sink. The bilge pump gets 12V power off the battery in the UPS that keeps the tank running during power loss. I hacked the UPS to provide fused 12V out and ran a power switch up to the the valve manifold.

Hacked UPS, notice the speaker wire for 12V out.

The process to change water is as follows:

  1. Shut off the filter pump and close off the valve leading to it.
  2. Open up the bucket fill valve to let tank water drain into the bucket by gravity.
  3. Once the bucket is full, close the tank valve and open the bilge pump and hose valve. Extend the extension hose to the kitchen sink and turn on the pump to drain the bucket.
  4. When the bucket is empty again, attach the extension hose to the faucet, open the bucket fill valve and close the bilge pump valve. Turn on and fill the bucket with fresh water.
  5. Once full, close the hose valve and open the bilge pump valve. Turn the pump on, which now just circulates water in and out of the bucket. Add water treatment and salt to the water, with the pump providing the mixing.
  6. Close the bucket fill valve, open the tank valve. Now the running pump moves the new saltwater up into the tank.

The whole operation takes minutes and saves us from breaking our back lifting buckets to the bathroom.

Here are some pictures of the system: