Are Water Changes Actually Necessary?

[Scuppers]

I just engaged in a wordy debate with a few guys who were insisting that frequent, regular water changes are absolutely necessary...yet could not explain why.

They could not give any specifics on what was being altered by the water change, that could not be done in some other fashion.

There was some vague talk of "replenishing and renewing" and "electrolytes", but of course you don't "replenish" anything with a generic water change. The only thing you're guaranteed to be adding is H2O, which does not age...and "electrolytes" sounds like a question of specific gravity, to be taken care of with sea salt.

The actual reason people used to change water regularly was that they were killing their fish with poorly-managed Under-Gravel Filters, and were fighting the nitrate buildup they were causing.

But that's no longer the case, thanks to deep sand beds, open-celled ceramic foam, planted tanks, et cetera. There are many ways to remove nitrates so efficiently that they can become TOO low.

So what reason is left?

What is the reason to do a water change?

And I mean some measurable, explainable reason. Something you can choose to do under specific conditions. Giving a timespan for doing them without reason is meaningless.

Since water changes place stress on fish and ecosystem, by altering the tank's self-imposed balance of micro-organism density, reducing the amount of nutrients, et cetera, water changes were never anything better than a necessary evil.

Are they STILL a necessary evil, and if so, why?

I'm with you Sir (Kazvorpal). A fish tank is an eco system where every effort should be made to ensure that the balance between the plant life and other living creatures is maintained. Conditioned water was just to replace evaporation.

From experience over many years I can honestly say I doubt I ever changed water, even 10% at a time, more than perhaps six times, and that mostly due to me introducing disease, via plant or fish, because I did not use my interim tank(s) for a long enough period.

Have to say though that I have only used U/G filters with air lifts and a small 'polishing' HOB filter. Mostly maintained 74 degs and Ph 6.8 in 55g community tanks. Have never once tested for anything else! Always strived to have an excess of plants. Used corys for keeping the floor clean.

I have just built a 75g and will set it up just the same. No fish will be going in until the plants have had two months, at least, to establish.

And, trust me, if I have a catastrophic failure or the system I am used to fails, I can eat humble pie and I will let y'all know.

 

[kazvorpal]

Unless you have the ability to do everything that Mother Earth does, you need to change water. I can not give you all of the minute ingredients in water that the fish use as I am not a scientist. I can tell you this, however, if you don't change water for a long period of time and then you change a bunch......fish die. That in itself tells me that the water changes, loses elements, and gains elements. The idea of water changes is to be able to maintain a steadiness of water quality. Adding salt, whether it is sea salt, iodized salt, or any other kind of salt can not add everything that is needed and it surely does not remove waste. This would be the same as saying you could live in an out house forever with the door closed and the stench and filth would not be there and you would remain healthy so long as you had some salt.

I got too busy to change a community fish tank once, for about a year and a half. I also only fed them (reliably) about twice per week.

In that period, I did not lose a single fish.

Deciding I may be "on to" something, I continued that treatment even when I had plenty of time. In the next two years, I lost one molly, whom I'd had for perhaps five years and seemed simply to be getting old and feeble.

So your claim that if you don't change the water, fish die, is only anecdotal. Perhaps that happened to you...but you don't know for certain that lack of water changes is what caused it...while I can say for certain that lack of water changes did NOT kill my fish, because they did not die.

Also, I was not the one who suggested electrolytes as a reason for water changes, I was saying that someone else claimed this...while claiming to be a scientist in a related field.

As for "removing waste", that is what the tank's own ecosystem will do, without any intercession on your part, if you set up the tank properly.

Most people, almost incidentally, end up with a tank capable of converting ammonia into nitrates and nitrites, and nitrites into nitrates.

That's where casually set up tanks usually fail. Nitrates generally need either plants or anoxic organisms to break them down. But we now know that there are many ways you can set up a tank to host those things.

And no, the water does not gain or lose elements. Spontaneous generation only happens on a quantum level, if at all. Again, this is too vague.

If there are specific elements, find out what they are, and let us know. Also, let's figure out how to measure them, and how to add/remove them.

You certainly don't ADD many elements by changing water, except the minerals that make water hard.

 

[msjinkzd]

Testing water hardness is pretty easy. There are also TDS meters, you can find some here.

I do test hardness, but not TDS. With over 40 tanks running, its just not feasible for me to test every tank consistently.


On the other hand, surely if your tank water is hard, your tap water is hard. Or are you concerned that your mildly hard water is accumulating into very hard water, via evaporation and replacement, or that other kinds of organic dissolved solids are doing the same?

My water is hard. And I have noticed if my water changes are late, spawning slows and coloring of the fish and their activity levels change despite no real changes in measurable readings of nitrate. I change the water (I guess diluting the accumulation) and spawning occurs and colors improve. Being as I keep wild caught species from many different countries, this is somethign I care about.

If so, how often do you do a change?

You know, I may actually buy one of those meters, if convinced that this is a serious health factor for my fish.

How frequently I do a water change depends on the amount of waste produced by my fish and their behavior. Some of my wild caught species get several very small changes weekly. Some of my domestics get 20-30% every other week. My big fish get weekly large volume changes. Most of this is based on observation as to their behavior, coloring, feeding and not always on quantitative measurements.

Because I have 40+ tanks runnign of fish and invertebrates ranging from 1/2" - 20+", there is no set rule for what is required for the tanks as a whole but I can say when maintenance has been skipped, breeding and color has been effected. Also, in wild caught fish specifically, the turnover rate in a body of water is much greater than we can achieve in a tank. Therefore organisms present in the water body (parasites, bacteria, etc) are much more dilute. When put into a tank, they have more stable conditions in which to multiply. Often you will get seemingly healhty wild caught fish only for them to develop hexamita or something a few weeks after introduction. Now certainly water changes don't prevent this from happening, but it can lessen an infestation.

 

[blue2fyre]

No water changes for years? Wow

What are your parameters? I'm curious.

 

[kazvorpal]

I do a 75% water change weekly on my 55 gallon. My fish love it and often spawn shortly after. I doubt they are stressed by it. I use to do a 25% water change weekly since I just had a bucket. Once I started doing larger changes my fish were happier and the tank just looked cleaner. My fish grow faster and are generally healthy when I do larger water changes regularly. So I must be doing something right.

I've even had fish heal from disease using large daily water changes alone.

Your fish do not "love" the water change.

They are triggered, genetically, to spawn by anything simulating a "rainy season". The sudden change in water conditions also does stress them. Nobody denies that changes in condition cause stress, more in fact than most conditions when stable.

In fact, stress actually triggers many fish's spawning cycle, as well. It's akin to how if your tomatoes are not subjected to enough stress, they will grow green and healthy, but bear no fruit at all. This is what happens if you give them high-nitrate fertilizer, for example. They grow bushy, green, healthy, and barren.

You are stressing your fish into spawning. This isn't even necessarily bad, but it shows how flawed inductive reasoning like "they make babies, so they must not be stressed" can be.

As for your tank/water looking cleaner, that's good for you...but never imagine that to be good for your fish. They didn't evolve in nice, clean water/lakebeds, but in healthily dirty ones. Many of them would actually benefit from your tank being draped with algae and other gunk, although personally I am not willing to sacrifice the prettiness of the tank in order to benefit my fish in that way.

Well, except in my marine tank. Saltwater aquarists often choose to let the sides and back of the tank get completely coated with gunk, and only clean the front, unless it's a "display tank", where we sacrifice ideally dirty conditions in order to show off our craft.

 

[12 Volt Man]

So far, four people have voted that they do water changes on a timeline...

But nobody has posted any explanation as to why.

to avoid old tank syndrome, where a gradual build up of wastes reduces your pH to very low and toxic levels. I have had this happen before with overstocked tanks. even with water changes, the pH would gradually drop over the week to levels that would cause big problems with my fish.

its common with people who never change their water too though, not just with overstocked tanks. used to see it all the time while at the LFS.

its not as simple as just the nitrate level, as plants can take care of that if you have a heavily planted tank with a light stocking level. the plants can take up more nitrate than your system is producing in that case.

but you still need to do water changes.

now, all of us have the fish friend who never changes their water etc and their fish are fine.

well, they are. for now. they are used to the high waste levels (which we measure as nitrates) and lower pH.

but buy a fish from the store, add it to the tank and the fish doesn't make 48 hours.

customer freaks out, brings you in the fish and a water sample.

what happened? my fish are fine! he or she says.

the problem is that the fish that were in the tank were used to the high levels of TDS. the new fish was not, and no amount of acclimation can stop this.

hence, the new fish doesn't make it.

the old fish are fine. for now. eventually the pH drops low enough and the nitrates can get high enough and you get lots of problems eg. fungus, popeye etc.

for long lived fish, water changes are important.

and when I say long lived, I mean 10+ years. not one or two.

most fish should live a lot longer than they do. and the reason is that people let the water quality slide, the fish get problems. and die early

but that is a whole other rant LOL

I change 1/3d once per week on my tanks.

 

[Somervell]

I voted, Kaz, as I do change my water on a cycle at more or less constant percentages. I am very interested in this thread and am glad that you posted the poll. I usually change as I remove solid waste from goldfish, and have simply done so at small percentages habitually. I will follow this thread avidly to see what others post.

 

[blue2fyre]

They do seem to enjoy it. They swim around and even right into the hose where the new water is coming out. My fish are more active and more colorful after a water change.

I have plenty of algae in my tank. It doesn't bother me a bit. My fish enjoy eating it. What I meant by looking cleaner is the water is very clear.

You still didn't mention at all what I had to say about fish growing faster and disease being fought off.

 

[Fishfriend1]

All of my tanks are a little cloudy except my tropical under stocked tank. That one has way to many plants and a good set of snail keeping it clean.

 

[Lab_Rat]

I'm too busy to pull peer reviewed articles and I don't have any desire to do so. If you want that evidence you can get it yourself. Just look up an IACUC proposal for housing of fish for research. They certainly do water changes.

In addition to the TDS that msjinkzd gave an example of, fish hormones accumulate if water changes are not conducted. This can lead to stunting and aggression. There is no commercially available test to the public to test hormone levels in a fish tank that I am aware of. So since we can't see them does this mean they don't exist? Are you going to tell me fish don't produce hormones? Or that hormone build up doesn't affect fish health and reproduction?