Marine Aquarium Water Changes: Don’t Postpone the Personal Payoff!

Part of my clan rejoicing in their "dose" of clean water

Part of my clan rejoicing in their “dose” of clean water

Yesterday, I finally got around to performing an overdue water change in my 125-gallon tank. Admiring the fruits of my labor afterward, I couldn’t help wondering, “Why on earth do I wait so long to do these when the result is always so rewarding?”

Actually, I know exactly why I wait so long, and it’s probably the same reason many of you do as well—sometimes life just gets in the way. Writing and editing projects begin to pile up, deadlines loom one after another, and I just don’t have enough time or energy left by the end of the day to squeeze in yet another project. Weekends usually find me catching up on articles or SWS posts or at least trying to squeeze in a little relaxation, so I don’t exactly relish the thought of doing water changes then either.

Still, whenever I discipline myself to push through and tackle this essential maintenance chore (which actually doesn’t have to be as challenging or time-consuming as I make it out to be in my head), not only do my fish and corals reap the benefits, but my enjoyment of the tank is significantly enhanced as well.

How so? First off, the dilution of all the bad stuff in the water and replenishment of the good stuff—like a rush of fresh air into a stuffy room or that first warm spring day after a cold winter—seems to bring out the very best in my fish. Never are they friskier or more vibrantly colored than right after a water change. They even seem to respond positively to the appearance of the vacuum hose in the tank, as if they recognize that it means clean water will soon be on the way. I don’t know whether it’s possible for fish to think this way, but their lively comportment in the hours and days after a water change seems to say, “Aaaaahhhh, that’s the stuff!”

The corals (just a few softies at the moment, though their numbers will be growing soon) tend to perk up as well, expanding to their fullest potential as if to display their gratitude for the boost in water quality. I’m sure they also appreciate the fact that water movement throughout the system is maximized after a water change because my regimen includes cleaning any algae or gunk buildup from the intakes and output nozzles of my submersible powerheads and sump pump as well as from the slots in the overflow and the nozzle for my sump return hose.

General visibility is also best in my tank right after a water change. Because the tank has windows facing it on all sides (our house has an absolutely preposterous number of windows, so they’re pretty much an issue in every room), all the panes are very prone to algae growth. So, right before siphoning out the dirty water, I give the panes a complete once over with my algae magnet, scrape any coralline algae or other tough growths from the glass with a single-edge razor blade, and gently clean the corners with an aquarium brush.

The net effect of all this is a crystal-clear aquarium filled with healthy, energetic livestock—not to mention, a proud, gratified tank owner. And you can experience this as frequently as you’re willing to perform water changes. Not a bad tradeoff!


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About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. Leslie Melling says

    Water changes are a bind and yes I am as guilty as anybody when it comes to putting off doing them however I have an item of equipment that lesson the load. I don’t think it’s available in the US or Canada unfortunately at least not yet. The equipment in question is a Reefloat AWC. You can check out the vids of it in action on YouTube. Here is just one the installation guide.

  2. There is no need to do water changes anymore, if you still do water changes you need to learn how to not do them by simple chemistry and carbon dosing.

    • Hi Zippy! Thanks for your input. I’m afraid I’m not quite on board with the notion that water changes are obsolete, however. For many hobbyists, the water change remains a tried-and-true, straightforward, easily comprehended method of diluting dissolved pollutants, replenishing vital elements, and promoting stability of water parameters. I don’t doubt the method you advocate is effective, but as with every aspect of this hobby, a lot of factors influence which particular technique/methodology makes the most sense for any particular individual.

  3. Do you allow free opinions against you to be posted?
    One time I posted a comment, but it was not posted after all.
    The comment that I have for this article, is that simply I never change water in my tank.
    I add water time to time due to evaporation.

    I have hardy fishes: fresh water figure 8 puffer acclimated to salt water, maroon clownfish , clarkii clownfish, six line wrasse. two hermit crabs.

    Long time ago like 20 years ago , I use to post at usenets groups like rec.aquaria….
    I use to keep a thread “maintenance free tank with tanganykan cichlids”

    • Hi Chip! Absolutely we allow free opinions to be posted, and we appreciate your doing so. Sorry your prior comment didn’t make it through. I’m not sure why it didn’t appear.

  4. I won’t comment on the no water changes, but Jeff I think your water changes are what makes those fern plants do so well in your tank.

  5. Hello Folks,

    I thought I would post my two cents on this subject. I’m with you on this for the most part Jeff. I run a forum and that means I’m online a lot reading posts and not just on my forum. The one thing I notice about posts with people claiming water changes are avoidable is the complete lack of information; I find it irresponsible.

    If you are an experienced enough reefer to keep a ‘successful’ aquarium without doing water changes, chances are you know how aquarist are and how short most peoples experiences end up being because of bad information’s and habits.

    Without the information about all the other things you have to do in place of not doing water changes one is left thinking ‘I should try this’! No one ever talks about the equipment, supplements, testing and so on needed for doing this. I never see anyone making these statements explain how this is really more cost effective in the long run for larger aquariums but to not bother trying it with smaller ones. Nobody talks about the problems that can accompany having to run GFO, carbons, and other supplements or the effects they can have on coral.

    It’s not unlike most people making claims online suggesting how great something is. I think before making mention of this being an option it should be made clear. Questions should be asked. This method is not ideal for most people especially new comers and I sincerely wish people would stop making it sound like a cure for tank maintenance in general. I think you would be surprised how many folks I see with bad or mismatched information because no one talks openly about it when they bring up not having to do water changes.

    Best wishes!

  6. I never do water changes in my salt water tank.
    The water looks so clean.
    I only have one peacock mantis shrimp.

  7. Just like taking care of your own health, you need to experiment with what works for you and what not. In my both 30 years of only fish keeping lake tanganykan cyclids or marine fish only tank, I never did water changes as many forums and shops rigorously recommends to do. Well if you like doing your way , that is fine. In my case, I like to have fish aquarium but I never like doing maintenance. My aquariums are super clean, not signs of green algae on the sides of the window, no special expensive lighting, no automatic water top on, just very low maintenance aquarium keeping. Are there any fish hobbyists in silicon valley, I can show it to you. Or maybe I can post pictures here. On a funny side, did your fish ever asked you “hey time to change water, I am dying in this pool of recirculated water”. Fish don’t talk, so why bother treating them like kings? If you like spending lots of time and money in this hobby that is your thing and that is fine. But it is not a must to change 25% water every 2 weeks

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