Has anyone successfully gone to no water changes?

  • #1
This is a subject of great interest to me. Can you set up and grow a tank without ever removing water?? I've never been a big water change person and most recently at my last apartment I had a 24, 30, 55, 10 and various nano tanks that I had running 3 years without ever removing water, only adding water to offset evaporation. I can share what i have learned but I'm curious about other experiences. I will profile the 3 big tanks for brevity.

55: cories, rasboras, hatchets, 2x cannister filters with one filer being cleaned out and re-set every 4 months or so. 48 inch T5 GLO light.
This tank did the best over the 3 years, but at the very end it turned the worst. This was a good example of the balance that is needed to do a no water removal tank. It ran well with slow but visible plant growth and good levels, nitrate stable and low. Tannins from driftwood I believe acted as a buffer and kept the fish happier, after about a year the tank had a weak brown tint that only grew deeper. I would go in and remove debris that was dead, and there was a snail and shrimp population to clean up. Eventually the tank "turned" and algae and the dreaded "blue green" slime emerged. I believe this was because the phosphate levels in the water eventually got out of balance with what the plants could absorb and created a situation where the plants were losing ground to slime and algae. This didnt happen until about midway through year 3 though. I had to vaccuum the whole tank at this point so strictly speaking i was removing water, but that was well into the 3rd year. I cleaned it like crazy and it stabilized a bit but never bounced back to how it was. No deaths in those 3 years!!

30: 3x electric blue acara, one dwarf bushynose pleco. One 30 gal backpack filter. finnex led lights.
This one was the most interesting I think and in one way was the only "successful" tank. It had plants but they got abused by the Acara and eventually there were a few stubborn plants left but mostly just java moss, a huge (half the tank) mass of moss. This tank also got quite dark with tannins from some wood. The moss spread out to create a "zone" where waste would accumulate underneath and be absorbed but not mix with the rest of the water. The moss seemed to stabilize the water parameters. I would remove moss to make room as it overtook the tank but it would grow back. At the end of 3 years, no deaths, no algae, no slime. Stable nitrate. the tank was not pretty to look at but it was "stable" and had clear water aside from being tannin stained.

24. 6x gardineri killies. One built in integrated filter (built in wall of tank) finnex led light.
This one started off ok but was essentially a long sloping decline. I believe the reason this one did not do as well as the others was simple. the filter did not create as many bubbles as the other tanks, phosphate and trace minerals built up and created an untenable situation for the plants. the first year or so was ok but this tank got blue green slime and algae about the one year mark and never really bounced back. i would clean the mess, and I may actually have tried a water change or two on this one, bu it just kept getting slime and algae. the fish were ok and the water was actually very clear, and acceptable on nitrates but plants would never do well and sustain growth to absorb minerals etc. No deaths but it was ugly and would not sustain plants other than a few crypts which mysteriously did ok, but never grew. I think the nature of the filter was a major factor. i added a sponge filter at one point to get bubbles in there but it only drew out the sloping decline. Still, no deaths, fish were happy.

So now ive moved and re-set the tanks. Still holding to my philosophy of not water removal but with the following changes:
I can already tell this iteration is gonna be much better-------

-Co2 on the 55 and the Acara 30
-Using RO water to avoid mineral buildup
-using Prime instead of Neutral Regulator----Both change the profile of the water but i believe the Regulator Phosphate buffers are an issue if the plants cant absorb the phosphate
-Cutting back healthy pants on a regular basis. with Co2 I get enough growth that this is necessary and i think removing plants is in essence removing solids from the water.

Love to hear peoples opinions. i know not doing water changes is kind of a crazy idea but i have had success (though not always "beautiful" tanks.)

What would your setup be and why if you could never remove water??

  • #2
I don't really do changes, per se, except when getting fish, mainly goldfish to grow. Turns our they secrete a hormone that regulates size in relation to their tank. If you do frequent, major water changes, it causes a distillation of that hormone, meaning it's okay to grow more. My "feeder" comets I bought at about an inch or 2 are now as big as koi (8-14 inches). The rest lose a lot of water due to evaporation, so I do top-offs about once a week. Keep in mind, I'm a bit unorthodox in that. I don't see any reason to do major water changes unless there's a problem in the tank.

  • Thread Starter
  • #3
I think theres this prevailing idea that the only way to remove nitrates is to do water changes but I feel like that the plants job to absorb nitrate
  • #4
Oh yeah, it's definitely possible. I usually do this as well, when I can help it.

Currently, my most successful tank is a 3 gallon walstad with several species of aquatic/riparium plants, LOTS of ramshorn snails, hopefully still 3 thai micro crabs, and 3 red dwarf coral platies. I haven't done a water change in over a year. The plants I added were COVERED in algae, and yet the green spot, slime, and brown diatom all died within 2 weeks! This is the tank now:

IMG_20230216_164943.jpg (Sorry for the terrible pictures. This tank always seems to evade good picture-taking lol.)
  • #5
I have two methods.

1) Open-top tank where I only top up water and never actually change the water. Minimal ferts, low bioload and low light. Weekly top up due to evaporation helps replenish minerals for plants. Never had algae issues.


2) 50% weekly water changes standard. Plenty of fish and plants. Tweak lights, ferts and Co2 until you get the perfect balance. I always make sure the tank can go a few weeks without water change if needed.

Everyone over time discovers their own method which works best for fish, plants and themselves.

The only wrong method is the one that doesn't meet the fish's environmental and behavioural needs.

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