Water Change Frequency and Why

[10 Tanks]

Hello. Have read quite a few articles on the subject of the water change. Here's my take. Half the water removed and replaced weekly. Why? The fish and plants constantly remove nutrients from the water, the longer the same water stays in the tank the more it reacts with oxygen in the air. The water chemistry is in a constant state of change. Your fish require a steady water chemistry to stay healthy. Look up the affects of oxygen on chemicals in your tap water. And, last and certainly not least, the fish are using the tank as their toilet. If I was doing all my "business" in my water, I'd absolutely want a lot of water to be removed and replaced and quite frequently!

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[AJ356]

I'm with you on this. I recently went over what Byron did for us here https://www.fishforums.net/threads/regular-partial-water-changes.471488/

As of about two months ago, I was doing about 50-60% every 7-10 days I think, but I've upped it now.

I am paranoid about water supply and potential one off contamination or the company "flushing the pipes", so I fill up large containers with about 180 litres of water (nearly 50 US gallons) about twice a week. With each new water collection, I'll water change only ONE tank first (the one that if I had to pick one tank for a wipe out, sadly it would be that tank, sacrificial lamb for the greater good), and wait until the next day before I do water changes on some of the other tanks. This is to avoid some kind of fluke wipe out of multiple tanks. In all my years of fish keeping, I can NEVER remember a water change that's caused issues in my tank, but the paranoia remains........ unless I had RO, then I wouldn't worry so much.

I don't have big tanks, the largest currently is a 4 foot shallow and long, I have 7 tanks up and running right now, ranging from 2 foot length to 4 foot length. Most are 3 foot shallow and long.

I'm doing about 50% a week in my tanks that just have one breeding pair

I'm doing about 65% a week in my tanks with a breeding pair and newborn fry (less than 1 month old)

I'm doing about 80-90% twice a week in my tanks with 0.5 to 0.75 inch fry.

I'm doing about 70% a week in my four foot tank with juveniles

On my fry only tanks with 0.5 to 0.75 inch fry, I take the water down sometimes to almost so low they would not be able to swim properly (not quite that low, but almost) - this is because I have a lot of fry in these tanks and the feeding is usually x3 daily

My fish have got accustomed to large water changes, no old tank syndrome here

I take my time with water changes, I'm always faffing about with something else and multitasking, which makes it easier on my fish as one water change takes about 60 minutes, so I am only gradually putting the new water in. The pH from my tap is always about 8.0 (post 24 hours) and the pH in my tanks seems to ride at about 7.4 or 7.6, so it reassures me that I am not dumping in 80-90% new water all at once. Not sure if a 0.6 PH change all at once would do any harm, but I don't risk it.

I spend hours and hours per week on my water change routine for 7 tanks, because before the new water goes in, it sits for 24 hours in a big tub with API Nitra-Zorb resin and a powerful internal filter to circulate the water around the bags of resin, this gets my tap nitrates down from about 30ppm to about 5-10.

I'm on a few Facebook groups and you wouldn't believe the amount of people who literally say they go years without doing a water change, and only "topping up", and we not talking Walstad method tanks, we talking regular busy tanks, full of fish, often with plants, but not always so.

 

[10 Tanks]

Hello AJ. I moved and wanted to back off on the time I spent changing the water in my tanks. I kept 11 tanks from 45 to 300 gallons until about six months ago. The fish were so healthy and always breeding, just because I kept the toxins out of the water through large, weekly water changes. I finally decided to rehome everything to a friend of mine who takes in fish and equipment and resells all of it. He has quite a business. Now, I keep one 55 gallon with some Minnows I took from one of our local ponds. Nice fish and they thrive in near pure water conditions. Our weather here is really nice most of the time, so the local fish are used to warmer water. I don't need to heat my tank and I just treat the tap water and fill my tank from the faucet outside.

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[AJ356]

Yes, I could see you were awol from the forum for a while. I'm glad you have the one tank. One tank is 100% better than zero tanks my friend

 

[GaryE]

I have 50 tanks, so time matters. All are very lightly stocked. In terms of numbers of fish, I often have 2 1.5 inch fish in 10 gallons. I'm a maximalist for tanks and a minimalist for stocking.

Two days ago, I did a top off on one tank, so yesterday, I did a water change on it. It was my first top off in a year, caused by the dehumidifier, which I moved. I keep a whiteboard on my fishroom door, and record water changes. I do 30% to 50% a week, though I have been experimenting with shifting to 10 days. This takes me 3 hours per week.

We can and should discuss the implications of the nitrogen cycle, and we should be aware of the other rarely mentioned processes in an aquarium. We discuss water changing a lot, because it's work and we don't want to do it.

The walstad method is another story, but most people who try it don't read Diana Walstad's well thought out and researched book, and just improvise something. Done correctly, it's an approach for extreme light stocking.

On forums, there's an awful lot of hoping someone, anyone, will free our consciences and let us happily permit our fish to stew in their own wastes. People also find reasons not to walk dogs, or clean bird and reptile cages. It's just how we are. I'm sure there are people who cruise the few remaining forums, and other forms of social media until they find someone who sounds authoritative and tells them what they want to hear. If we look in our tanks, we need regular water changes. If we look inside our heads, well maybe not, because, you know...

I started in the hobby 60 years ago when water changes were not done. I've seen how both approaches work. As far as stability goes, my dechlorinated tapwater is my baseline. It's clean water without nitrates, and fairly soft. I keep fish that thrive in such water.

Water chemistry can change quickly, so I go with reasonable water change frequency so it won't have time to diverge from the tap values. I know my pH and hardness, and as long as I don't allow minerals in the water to be used up, different minerals to accumulate from substrate (if I make a bad choice in my decor), etc. Frequency is for stability. Volume is for water quality.

I filled four previously fishless tanks with fry from 3 different egg laying species yesterday, so I take that as an indicator it works.

 

[raylove]

The idea that fish are swimming in their own waste is obviously true to a point but I believe it's a little exaggerated.
Freshwater fish do indeed produce a large volume of urine, however, this is largely to offset the effect of osmosis. A fishes internal chemistry is 'saltier' than the water they are in, so the water passes through their skin in an attempt to dilute it. This is why when a fish is sick, that process can break down causing their body to swell as it takes in more water than it can expel. The result - pine-coning. It is also why salt baths can appear to help, because it reduces the differential between inside and outside, thus reducing stress (unless the underlying issue has been resolved though, the problem will probably come back when the fish is returned to fresh water).
What this means is that whilst fish produce a lot of urine, it is very weak. Plants and other natural processes will deal with most of it in a lightly stocked tank so, yes, they are swimming in their own waste, but it's at a far lower concentration than we might imagine. It is not like us swimming in our urine!
Other pollutants do build up and plants and other natural processes will remove other essential minerals, so water changes are of course necessary. I limit mine to 10-15% per week which has proved sufficient for decades. My tap water is high in nitrates so the parameters in my tanks are better than the fresh tap water - at least for the things I can test for.
Once or twice a year I have a bigger clean up which can result in a 25-30% change.
I get more algae on the glass for a couple of days after a larger water change (presumably due to the high nitrate). It's a bit of a balancing act but our thinking can be distorted by imagining fish are swimming in neat urine - if the water doesn't smell the level of urea is surely very low?

 

[GaryE]

The swimming in urine image is a bit of a marketing type one. Grossing ourselves out makes a point. But it's there, with hormones, excreted foodstuffs, decaying plants, etc. In a large enough, well stocked and planted tank, there is an issue with what is removed as with what is added. The combination changes the water chemistry, and assuming we have cycled tanks, that's an issue.

In the pre water change era, in tanks with a little scraggly Elodea, it was possible to have yellow tinted water. I heard those discussions. It was seen as another reason to use charcoal/carbon. When I began trying these new fangled water change ideas on my tank of yellow sunset variatus platys, I completely ruined their camouflage.