Aquarium Water Exchanger

If you want happy fish you’re going to need to do regular aquarium maintenance. Part of this is exchanging a portion of the tank’s water on a regular basis. [Bill Porter] came up with a water exchanger that means less manual labor, but makes the process just a bit more complicated.

So, what he would do before is fill a few buckets from the aquarium and dump them down the toilet. Then mix up a few buckets of salt water and add them back to the aquarium. This meant carrying several trips worth of heavy, dripping buckets through the house. What he has now is a gravity fed system into the orange bucket with a bilge pump to evacuate the old water from that bucket into the kitchen sink. The bilge can then be used to circulate water through the aquarium and the bucket, while filling with a hose from the kitchen sink and mixing in salt and chemicals. Less trips, no drips, but you’ve got to know what you’re doing with all of those valves.

We love seeing aquarium hacks like [Bill’s], or cooling the tank lights while heating the water, or just a fancy lighting setup in general. So if you’ve got some of your own, don’t forget to send in a tip about them.

25 thoughts on “Aquarium Water Exchanger

  1. Yes the PVC glue was fish safe and I ran many gallons of water through it before installing it.

    All parts of the build were ‘Fish Store Owner Approved’ by a local fish store owner and friend. I wanted to do this but was nervous as heck to make sure what was fish safe or not.

    This has been running for a year now with minimal problems. Only fish casualties were from parasitic disease, and stopped after I added a UV sterilizer to the flow.

  2. It’s drinking water safe, so it’s safe for aquariums. Most reef tanks have a ton of PVC (and PVC cement) involved in the sump plumbing; you might see the occasional fish a little tipsy if it hasn’t been allowed to cure thoroughly :-), but outside of that, it’s quite safe.

  3. This is cool. Now put servos on the valves and automate it fully.
    But on the other hand, why couldn’t you just run the hose from the tank to the drain, then reverse the hose from the tap to the tank. Mix a pinch of salt in the main tank slowly.

  4. @Andrew

    I wanted to automate it, but it was cost-prohibitive for me.

    And you seem to have little experience with salt water tanks. You have to mix the water with salt and treatment before you put it in the tank, or it will stress/kill the fish. And it’s more then a ‘pinch’ it’s more like a cup of salt per two gallons water.

    You also have to treat the water before you add salt to remove anything your city adds to the drinking water and fix hardness and PH.

  5. If you want it to be safe, I would avoid PVC completely – or at least flexible PVC. To make PVC flexible, you add in plasticizers.

    About 30% by weight is plasticizer.

    Usually DEHP or other fairly nasty phthalates. The same kind of phthalates in cheap vinyl sex toys (and some medical devices). Really, really nasty stuff for people – let alone for fish which are even more sensitive due to their smaller size, among other factors!

    Yes, you can buy fish grade or potable water safe PVC hose but I don’t personally think those are truly a good idea. Better than industrial grade tubing, sure but still a good idea? No way.

  6. Oh – as to automation:

    Get some “ASCO” brand “Red Hat” type of valves from ebay and a simple arduino (and possibly some relay) would control these pretty well. Or you could go with actuated ball valves if you wanted to get really fancy.

    Looking at a hundred bucks or so of parts though – might be excessive for this application.

  7. I used to have fish but the cleaning and water exchanging became to much for something no one in the house appreciated. I can definitely say something like this would have made a HUGE difference. I probably would have screwed up the valves a couple of times but hey.

  8. I think everyone who has fish wished that it was automated.

    To be honest, the best systems I’ve seen involve trickle filters that have one of those float-valves in the sump to top up evaporation. Just have a valve for waste water and let it trickle or dump a few gallons a day and the top-off system will replace the old water with new water seamlessly. Completely automatic and really cheap (aside from the trickle filter…)

    Your system is great though and doesn’t rely on plumbing.

  9. Nice project, Bill! I like how you used the 12V power from your UPS. I see some robotics on your site too, I’ll check it out fully later. Are there pictures of your actual aquarium somewhere?

  10. Being an addicted reefer and an avid DIY’er, I really appreciate a good saltwater hack; especially anything that makes maintenance easier.

    I have my water 100% automated. I’ll explain my setup so non-saltwater guys understand the setup.

    The way most systems run is with two tanks – one has your fish and the other has your equipment and sits under your main tank, usually refered to as a sump. Water gets pumped up to the main tank and then overflows from the main tank back down into the sump through a hole drilled through the tank and some plumbing.

    My system has a third tank for water changes. Water gets pumped up to the water change tank my a separate pump and overflows into the sump. There are three float switches in that tank, one three inches from the top another one inch below that one and the third one inch from the bottom.

    At a set time my controller will shut off the feed pump for a minimum of one minute, in that that time water will siphon back through the pump but because of the height of the nozzle will only drop just low enough to rip the top two floats. The first will keep the pump off until the water change is complete. The second activates a second pump that will pump water out of the water change tank and into the drain until the water level reaches the third and lowest float switch. That switch will shut off the drain pump and activate a third pump that will pump fresh saltwater from a reservoir into the water change tank until it reaches the top float switch – at which point that pump shuts off and the circulation comes back online and a water change is complete; the whole thing takes about 5 minutes. My only involvement is making 180 gallons of saltwater every 9 weeks.

    One more thing; Bill – do your fish a favor and get a RO unit. The chlorine in the tap water is the least of your concerns. Flouride, Nitrate, Phosfate, Copper and countless other items in your tap water can only be removed with a good Reverse Osmosis/De-Ionization system..

  11. I keep my fishies clean & warm and my PC cool by filtering the water through the floor, layered gravel, sand, activated carbon, and a HEPA filter, which circulates through my system and returns back to my fishes as a warm rain. makes neat saltcicles too!
    .. jk obviously, which you should have caught at the mention of HEPA. actually the cooling system in the pc i’m typing on is a Socket A cooler, copper base, aluminum fins, which came with my ~2ghz socket A athlon, but is held tightly against a socket 939 cpu (64 bit athlonxp4000+)with that copper wiring that is in your walls, which is wrapped around the bolts that held the original heatsinkmount to the board, which are screwed in so far that i had to drill holes in the motherboard pan to be able to mount it in the case.
    but i would rather set up a watercooling aquarium so it wouldn’t have to clock itself to 1004.53mhz to keep in the 35-41C range, or maybe it’s just doing that because it’s installed in a half-fried motherboard, running a 32 bit OS instead of 64, etc. but i’m going to see how far it overclocks before it explodes since no fish will be harmed in the process.
    reasons i did this? had no spare socket 939 heatsink, didn’t want to buy, had spare 939 cpu, half-fried motherboard, but with oC capabilities,
    what’s that? STFU? ok.
    nice chumbucket you got tharr.
    use to use the exact same equipment for ‘beer bong’. Seriously. including the red/white pvc valve thingy, and the hose. no glue though, perhaps there was ductape involved, but i remember more like.. pressure coupling or something. AKA sliding stuff on other stuff really tight so there’s no leaks.

  12. Man, people are so critical here.

    I used to work for an environmental company that did testing for the EPA using live fish. All of fish tanks, equipment etc. was in some way or another connected with miles of PVC. It’s safe, and there are special glues that are also safe.

  13. Buddy of mine did this years ago for his reef tank, but it was completely automated. He had a makeup water creation tank from a pair of 5 gallon stainless soda kegs. salt is metered in, a mixing rod blends it as the RO-water is added and then it sits for 24 hours before the water change out is ran.

    Not really a “Hack” but simply using normal industrial process ideas on a small scale.

    I did this for a 95 gallon freshwater setup as well, but all I needed was one solenoid valve to divert the pump from filtering to empty the 35 gallon sump. I could empty faster than the water makeup could fill it, so I simply pumped it out, shut off the pumps, wait for the float switch to activate showing it was above safe level and restart the pump. Hard part was plumbing the water and drain to the tank location.

    Freshwater you can use simple soda soloniods. Saltwater my buddy had to make arms to move plastic valves as you cant have any brass in stream for saltwater. His tank monitor and AMX processor did all the work even reporting PH and salinity.

    Water change was easy, his reef motion system was cool. he used a pump to make waves in the sump and had the sump hydrostatically connected to the tank via underwater spray bars. it made the water slosh back and forth simulating wave action.. His corals grew so fast he was giving them away and selling fragments weekly at local shops to cover his tank expenses. (Plus he had 3000 watts of metal halides abov the tank.)

  14. I have some aquarium related projects that I am going to be putting up soon. I wanted to thoroughly test them and get all the bugs worked out before making it public. So far they have been working over 2 months without a bug so about ready. Uses pics, one wire devices, relays and has an lcd display.

    for control valves a really cheap source is sprinkler valves. Connect them to a wall adapter and a relay and you can control water easily.

  15. @mike

    so very true. Sometimes people with aquariums are a little over protective. For example they often quote the 100% silicone being sold in caulk guns as not aquarium safe and needing special aquarium safe silicone because the label reads not recommended for aquariums. The reason that is there is because they do not want to be sued if someone uses it and the tank fails. Some even get hung up on the , it will leach into the tank because it is acetic cured, failing to realize that when dry silicone doesn’t have any of the acetic acid left.

    The aquarium supply companies make a killing off using everyday plastics and chemicals and re-labeling them fish safe.

  16. @Bruno goncalves

    O man, quite a setup, but would be mucho overkill for my modest 40 deep w/ canister filtration. I like the manual premixing of the saltwater though, I’d be too nervous about an automatic system that mixed the water screwing up and killing stock. RO would be nice I had the money, but until then I’ve been ok with treated tap water.


    I approached my fish store guy about using sprinkler valves, and he said it was a no-no for saltwater systems. I don’t remember the exact reason, it was over a year ago.

  17. We do the following:

    1) Mix new salt in holding bin ahead of time
    2) Put a sump-pump with attached hose into tank, drain into a sink via hose
    3) Move pump into holding bin, point hose into tank, refill.

    Using a sedra 9000 I can change ~ 40 gallons of water in 10 minutes.

    There’s one or two drips and the heaviest thing I have to carry is the pump. It’s kind of like Bruno’s method but a bit more manual.

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