Are Water Changes Actually Necessary?

[petluvr]

I do water changes for the same reason I wear underwear 'cause my mother told me so
It just seems to me that by observing my fish you can always tell when it is time for their 50% weekly water change as they start to "slow-down" for lack of a better phrase.

 

[captaincaveman9]

The dissolved organic waste from the fish would be my biggest concern. But the easiest thing to "measure" would be excess phosphates in the water. Granted the most noticeable result from high phosphate is algae growth. The other measurable build up is nitrates. Obviously, nitrates in high enough quantities are toxic to fish. So, knowing the basics of the nitrogen cycle (I first learned this in freshmen high school biology), ammonia is broken down to nitrites, and then broken down to nitrates. obviously ammonia and nitrite are much worse for the fish. One worry I have with never changing water and the excess buildup of phosphate and nitrate in the water, you leave less room to dissolve oxygen in the water, raising the possibility of growing anaerobic bacteria. and once you get that growing in the water column.

I do a 25% to 50% water change weekly based on my nitrate levels.

 

[kazvorpal]

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.

So far, this is just an assertion.

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.

Oh, absolutely, if the tank has accumulated high nitrates. Many fish can thrive in nitrates up above 100, if it got that way very slowly and they're used to it. The sudden CHANGE in nitrates, for the new fish, whose LFS environment may have been nitrates around 20, can be fatally stressful.

This is also why water changes should be avoided, unless needed:

It's the change that produces stress. Water changes must (else why bother) alter water conditions. The fish may well be used to those conditions.

If you once worked at an LFS, then surely you had people come in with mysteriously dead fish, and learned they'd recently done a water change. Or perhaps you didn't pay attention to that, because you weren't expecting it to be causal...but it can be.

In fact, I once worked at an LFS, but unfortunately as staff, not management. We got a new manager, who immediately changed all of the tanks' water by...I forget if it was 25% or 50%. We then lost about sixty percent of our fish, which had not been a problem previously, with rarer ten percent water changes.

The sudden change in water conditions killed the fish.

CHANGE, in either direction, can do it.

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.

Obviously, some amount of acclimation COULD fix that. "Used to" is not a static condition.

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.

That is an old-school assumption.

If you have a deep sand bed, or a mud filter, or a plenum, or a few plants and a protein skimmer, or ceramic foam plates in your tank, then the nitrates do NOT build up, but in fact can be problematically low.

for long lived fish, water changes are important.

You have given perfectly reasonable explanations for why, in specific circumstances, water changes are important.

But not why they are generically, universally important.
[/QUOTE]

 

[kazvorpal]

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.

It's not that your fish are spawning less because they're stressed from minerals. In fact, they're not stressed enough to spawn.

What is actually happening is that your water change places stress on the fish, simulating a change in seasons, that genetically triggers a spawning.

It is the actual changing of water, not the alteration of hardness or nitrates, that causes the spawn.

You make plants bear fruit by stressing them, and you make fish spawn by stressing them. A subtle stress, to be sure, but that's still what triggers reproduction in many forms of life.

This illustrates how nebulous "I guess it replenishes something" logic can actually be missing the real cause.

 

[petluvr]

I can foresee the fate of this thread.....and it's not a good one

 

[Fishfriend1]

"You have your way. I have my way. As for the right way, the correct way, and the only way, it does not exist." - Friedrich Nietzsche

 

[kazvorpal]

The dissolved organic waste from the fish would be my biggest concern. But the easiest thing to "measure" would be excess phosphates in the water. Granted the most noticeable result from high phosphate is algae growth. The other measurable build up is nitrates. Obviously, nitrates in high enough quantities are toxic to fish. So, knowing the basics of the nitrogen cycle (I first learned this in freshmen high school biology), ammonia is broken down to nitrites, and then broken down to nitrates. obviously ammonia and nitrite are much worse for the fish. One worry I have with never changing water and the excess buildup of phosphate and nitrate in the water, you leave less room to dissolve oxygen in the water, raising the possibility of growing anaerobic bacteria. and once you get that growing in the water column.

I do a 25% to 50% water change weekly based on my nitrate levels.

I hate to flood the thread with posts, but feel responsible for honestly addressing anyone's points. Perhaps I should combine replies into single posts...

Anyway, phosphates are a perfect example of how complex these things can be:

In fact, the algae do indicate available phosphates, but not necessarily accumulating or overly high phosphates. Why? Because the algae is consuming it. This locks it up, keeping your water healthier than it would have been without the algae.

If, on the other hand, you rush out and buy an algae eater, or (shudder) use a chemical algae killer, you RELEASE those phosphates back into the water, which does indeed create bad conditions (that are rapidly altering) for the fish.

Algae is actually a good part of the ecosystem of the tank. It can consume phosphates, nitrates, et cetera.

If one does not like the look, one can physically remove the algae, which is way better than having it eaten or killed, or one can simply add plants to the tank, which will outcompete the algae for those nutrients.

 

[bghill]

I voted for "when it is required" altough this will be a new way of doing things.
In the past, I too have thought regular weekly changes were the best way to go and have done that. As I learn more about this hobby I am questioning that theory and and going to try to not do as many water changes.
My reason for this is an ongoing battle with cynobacteria I think is due to low nitrates and plenty of friends bugging me about my water change schedule. (As in they do not do weekly changes either)
This is, and hopefully will continue to be, a very interesting thread.
Just wondering what large, public aquariums do about water changes. Anybody know?

 

[Lab_Rat]

This is also why water changes should be avoided, unless needed:

It's the change that produces stress. Water changes must (else why bother) alter water conditions. The fish may well be used to those conditions.

If you once worked at an LFS, then surely you had people come in with mysteriously dead fish, and learned they'd recently done a water change. Or perhaps you didn't pay attention to that, because you weren't expecting it to be causal...but it can be.

In fact, I once worked at an LFS, but unfortunately as staff, not management. We got a new manager, who immediately changed all of the tanks' water by...I forget if it was 25% or 50%. We then lost about sixty percent of our fish, which had not been a problem previously, with rarer ten percent water changes.

The sudden change in water conditions killed the fish.

CHANGE, in either direction, can do it.

That is called old tank syndrome and is well known. If done regularly and frequently, crap the fish get used to won't accumulate. Anyone who has had any experience in fishkeeping knows if you suddenly alter parameters, even if it's for cleaner water on a neglected tank, you will stress the fish.

I do 50% weekly water changes on all of my tanks. I've never noticed any stress from my fish during or after a water change.

An anecdotal example of the benefit of water changes is my brother's tank. He was bad about doing water changes, might do them once a month. Since I got on his case and he stepped them up to weekly changes (starting slowly and working up) his fish have had noticeable growth and one species started spawning. All in the span of 4 weeks (Thanksgiving to Christmas).

 

[snoopy65]

Generically and universally they are important for the health of the fish. I will give you an example. One year ago, I was given 5 - 3 spot gourami from Fordtrannyman as a Christmas RAOK. There were 2 males and 3 females, all from the same spawn, all received at about 1" long. I kept 3 - 1 male and 2 females and gave a cousin the other 2. I had a 65 gal hex that I tore down that had 2 cycled magnum 350 canister filters on it. One filter I put on a 30 gal tank and put my 3 gourami in it. The other canister I sold to the cousin. I took it down the street to their house set it up on their 30 gal tank and put the 2 gourami I gave them into the tank. Both tanks had low light plants, as well as hornwort as a floating plant. I did weekly water changes and they still have not done any. Guess what....my three fish were 5" this past fall when I gave them to another member on here and the 2 I gave to my cousin.......were barely past 2" until they died a couple of weeks ago. My cousin was quite proud to have kept them alive for a year........I have tried and tried to stress water changes to her too, but some people just don't get it.