Is this okay instead of regular water changes?

I'll be getting a pair of juvie axolotl soon, and I want to make sure I've got things planned out correctly. First of all, let me explain a bit of background behind my thoughts on water changes:

I have had 3 aquariums in the past; a 10G pseudo-replication of a local river ecosystem, a 10G guppy setup, and a 75G cichlid setup.
The guppy tank was my first, and I went with the traditional approach of weekly ~20% water changes as this seemed to be the norm. The tank was very successful, but it was a huge pain to maintain. And despite the frequent water changes, calcium and mineral deposits from the tap water built up along the edges of the water and all over the filter etc. very quickly and I had to constantly scrape it off. It was fun to study guppy genetics by breeding, but eventually I ceased to learn from them and passed them on to somebody who would.
When I started my next aquarium project, the river-in-a-box, I initially filled the tank with water from the river I was studying. After that, I never did a "water change" at all. As the water evaporated, I replaced it with RO water(little to no minerals). Most of the minerals left behind from evaporated water stayed behind, so I didn't worry about that. When the pH started to change(usually once or twice a year), I took it as a sign that mineral levels were getting a bit low, so I supplemented with some more river water. I kept that tank going with this method for four years before returning its occupants to where they came from because I had to move. All were happy and healthy the entire time(except for the baby fish, which were preyed on by almost everything...)
I took the same approach with my 75G cichlid tank, but with treated tap water rather than river water. I was very happy with the results. No time consuming water changes were ever necessary, I never had unsightly mineral deposits to scrape off everywhere, and all my fish were healthy. I no longer own the aquarium(I sold it at the same time that I released my river critters), but the new owner has been using the same strategy as me. It has been running for 8 years and still contains all the fish that were in my initial setup, perfectly healthy.

So I have 3 questions for users here:
1) What purpose does regular water changes serve that RO top-ups does not? I assume there is an advantage to water changes, since it is the norm. But I never had any issues with water quality at all with my method, and it did seem much easier to me.
2) Is it safe to use my method for my axolotl tank? Or is there something about their biology that would make normal water changes a better choice?
3) If you think I should definitely do regular water changes for my axies, do you know of an efficient way to do it? In the past I have used siphons or pitchers to move water around.

RO water will kill amphibians.

xxianxx said:

RO water will kill amphibians.

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Oh??? Can you elaborate on that? What does it do that is harmful? I was under the impression that RO water should be mostly H2O(purity varies from system to system, of course)...

EDIT: I should clarify that I did not intend to start a tank with RO water. It would be started with treated tap water, and only topped up with RO water as it evaporated, then occasionally supplemented with more tap water to keep up mineral contents. I know that the aquarium water must have minerals in it, but the majority of the water minerals stay behind after evaporation, so even with RO water top-ups mineral concentrations shouldn't be a huge issue. If there is another problem with RO water, please let me know.

Topping off with RO water would be perfectly fine, along with the added benifit of having a consistant mineral content in the water. However, it does not take the place of regular water changes, which remove/dilute wastes within the water column. Topping off water doesn't remove any wastes, it just replaces evaporated water. For changing water, I use an aquarium siphon with a gravel vac attachment. The only way RO.would be harmful is if was the only water in the tank, in which case the lack of minerals would cause the animals cells to flood through osmosis.

In short - amphibians need a higher mineral content than fish, so RO water isn't good. Hard dechlorinated tap water is best.
Water changes remove waste (nitrates) that topping up doesn't. You can reduce nitrates by using plants, but it still doesn't help remove poop. I use a siphon to remove water and poop at the same time - takes me less than an hour a week to do a 25% water change.

Thanks! I'll be sure to do weekly water changes. I'm cycling the tank(40G long excessive?) currently with feeder fish(they won't be in there when the axies move in).

I always thought it was the bacteria in the filter and throughout the tank which took care of all the chemical wastes. I never saw any spikes in my previous aquariums(tested weekly) and I didn't have any plants. But I never had amphibians in them!

Haha messy creatures indeed! :grin:

I really love those moss balls, but I've never used any myself. Do they need any sort of maintenance, or could I just throw some in the tank?

Sounds like you're on the right track! 40 gallons is sufficient for 3-4 adult axies, but yeah like everyone said they are very very messy creatures with a heavy bioload. I don't think you can get away with doing no water changes, but maybe with enough plants you can reduce how often you need to change the water. Just be aware the longer you wait between water changes the less you can change a time. Water chemistry changes over time in an aquarium and so after one month the water will be significantly lower PH. Regular water changes keeps it close to your tap water chemistry meaning you could even do a 50% change if emergency calls for it. If you haven't changed it in a month though, you'd have to change 20% or less at a time

I run two of my tanks with minimal water changes, only topping them up with water from a dehumidifier (esentially distilled and similar to RO). Both have a very thick substrate and are clogged with plants.

You have to have a system which removes the breakdown products of the food you add. Nitrogen in the standard aquarium setup is only processed to nitrate and builds up. A heavy planting and anerobic bacteria in a deep base can deal with this. I remove substantial quantities of plant on a regular basis and perform at least monthly checks on nitrate levels.

At the other extreme I run some tanks uncycled with water changes at a frequency determined by ammonia levels and the pH and species tolerance.

layna said:

"Moss Balls in English, is a species of filamentous green algae (Chlorophyta) found in a number of lakes in the northern hemisphere."

You want to look for marimo moss balls, you can buy them in all sorts of sizes, but they grow quite slow.
Yeah just make sure to quarantine them in a tub of old tank water for a couple of weeks, then throw them in your tank

marimo moss ball | eBay

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I never would have thought of getting them on eBay! I should get some now and let them take part in the cycling process. I'm not getting my axies until January, but I'll let you guys know how everything goes