Any real reason for water changes in well planted tank?

[Fishboy_Max]

I know this sounds dumb, but is there really a reason to do a water change once you have a established tank that is well planted?
My 30gallon square has been running for 4months with fish being introduced 3months ago.
My ammonia is 0 my nitrate is 0 my nitrite is 0.1, and this is after 3 weeks without doing a water change.
I did one this morning of course but for the future is there really a need to do weekly water changes instead of monthly just to clean the filter?
My bioload is 10 ember tetras 1 female juvenile gourami 5 cory (is it cory or cories for plural) and a medium sized mystery snail.
I don't mind doing water changes but wasting 25l of water every 2 or so weeks is not so appealing.

 

[Colin_T]

You do water changes for a number of reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.
3) to keep the pH, KH and GH stable.
4) to dilute nitric acid produced by fish waste and food breaking down.
5) to dilute stress chemicals (pheromones/ allomones) released by the fish.
6) to dilute un-used plant fertiliser so you don't overdose the fish when you add more.

 

[GaryE]

We have a problem in this hobby - I think of it as "ammonia goggles". We use test kits that measure almost nothing that's going on, and we we focus only on what we can see. Nitrite/nitrate/ammonia, and, with other easy test kits, pH.

Once a well planted tank is running, we don't need to test it for the "cycle". The nitrogen cycle is very stable. But the cycles that minerals and plants have going, that fish and minerals have going? We don't even know how to look at them. All the processes that go on are important, and we understand one process...

I wish I could tell you how the minerals and components of my water that I get from the city analysis works, but I can't. My water works differently than it did in my last house, 900km west. It has the same basic test kit numbers, the same TDS, but different components adding up there. Which ones are used by fish, and which by plants? I'm not a biochemist, and only know enough to know what I don't know.

I see different fish breeding, different algaes growing, and enough to know I have learning to do. Since I don't know exactly what's going on, I change 30% weekly and the system rolls on successfully. If I slack, I can sometimes see there are parasites lurking (oodinium spp - they love softwater and any decaying food), but only if I miss water changes for more than 2 weeks. The cycle? I couldn't care less - I don't own a test kit for that and haven't for ages. That's a minor problem in the grand scheme - a fatal problem early in the aquarium process, but a minor issue once the tank is established. I change water for more than that.

One of the most important things I change water for is fish chemical communication. Corydoras, for example, will kill themselves in small bags because their warning hormones happen to be toxic. I've seen fish go into fright behaviour for no reason I could see, and I've solved it with a water change. In 'dirty' water, certain behaviours change, sometimes radically. For most fish, evaporating pools of still, unmoving water are the peril of the dry season. They have adaptations to stay alive as they wait for the rains. I don't want those adaptations to kick in, so I provide life giving rains. It's easy to do.

 

[Slaphppy7]

Water Changes and Water Quality in Aquariums – Advanced Aquarium Concepts

advancedaquariumconcepts.com

 

[Fishboy_Max]

Hmm, I see all of your points, thank you!
For some reason all this went over my head even though I'd heard of most of it.
I'm glad I asked, again thank you all for the answers.
But if I may ask, there are certain YT I've seen just top off water from evaporation (I know evaporation doesn't remove a large amount of chemicals in water) over doing a water change and was just curious how it worked (these are some large channels aswell).
An example would be one of my favourites MD Fish Tanks. Who states in multiple occasions that he never does water changes.

 

[Slaphppy7]

Topping off does nothing to remove pheromones & allomones that the fish produce; and can cause build-up of detrimental residues

It also does nothing to remove detritus/dirt/mulm from the substrate

 

[Byron]

I cover this issue in depth in an article pinned at the head of this forum section. Here's the link.

Regular Partial Water Changes

Byron Hosking November, 2010 (rev April 2021) Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here. One frequently reads of products that will reduce the need for...

www.fishforums.net

 

[GaryE]

Honestly, if you want to have popularity and followers, tell people what they want to hear. I would LOVE to never do another water change. If I could produce a halfway sensible reason to never do another and sell it here, my "likes" would go through the ceiling.

I started fishkeeping in the "water changes are bad" era, when dirty water was seen as having magical properties. I keep seeing things try to swing back to that, as 'no water change' gurus come and go like the tides. They're wrong, and usually have pretty short popularity arc, even shorter than their ability to answer important questions about small bodies of water with fish in them.

 

[Colin_T]

When water evaporates, it is pure water that evaporates and all minerals, nutrients and chemicals are left behind.

If people don't do water changes and simply top up evaporated water, the pH eventually drops, nitrates go up, and the water turns yellow from nitric acid. The mineral content in the water also increases. Some fish will live in this sort of environment for 6-12 months or even longer, but most fish die. When someone does a big clean on this tank, they often kill a heap of fish in the tank due to massive changes in water chemistry.

People who advertise not doing water changes, are not caring for their fish properly and have no interest in helping others keep their fish alive for a long time.

There is an exception to this and it is a coral reef tank. If set up properly and there is protein skimmers, calcium reactors and other equipment on the tank that removes chemicals and nutrients, and you add mineral supplements daily or weekly, and you have a sump/ refugium with lots of macro algae growing in it, them you can add distilled water to replace evaporated water and not do water changes on a regular basis. But this is risky and the entire system can collapse if you miss out on one thing. So most people do water changes, even if it's only once a month.

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There is another reason to do water changes, which I forgot about in my earlier post. To remove tannins from water.