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Can a WC kill our fish?

cupofjoel

Fish Crazy
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I recently came across a video that posed this question: Could Water Changes kill our fish?

The premise of the video is that when we do a water change we usually clean our media and vacuum our gravel. This will cause an Ammonia and Nitrite spike that will stress out our fish that eventually can lead to fish death.

Thoughts?
 
Changing water is never a bad idea, stirring up substrate can release organics into the water column that can be detrimental which is why its important not to stir up substrate after a water change but during ,the goal is to suck up and remove that stuff. As for media ,replacing filter media destroys the beneficial bacteria on it, better to just rinse it off in a bucket of tank water. So yeah killing beneficial bacteria in ones media can lead to ammonia spikes. Water changes good! Killing beneficial bacteria bad!
 
Water changes can kill fish if there is no oxygen in water, sometimes stirring substrate up can kill fishes as @utahfish said
And yes, my one of my fish died because I stirring up substrate during water changes back then.
 
You shouldnt clean the media AND do a large water change on the same day. You could do a wc and then a day or two later perform the media cleaning if it is needed. I usually only clean the media once every three weeks.
 
Yes water changes can kill fish but only if the new water has chlorine/ chloramine in; or the new water has a different chemistry to the tank water; or there is a significant difference in temperature.

If you use a gravel cleaner when you do water changes, you can do big water changes and you won't harm the fish because the gunk in the substrate will be drawn out of the tank via the gravel cleaner.

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If you don't do water changes, you get a build up of waste products in the water and these encourage harmful microscopic organisms to grow and these affect the fish. The pH goes down and the nitrates go up and this weakens and can kill the fish.

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As for ammonia and nitrite spikes, that is unlikely to occur if you have an established biological filter and maintain it regularly and properly. Doing a water change should not cause an ammonia or nitrite spike.
 
I agree with @utahfish, mixing up the substrate while doing a water change might lead to complications.
 
My guess is that there are those who don't do proper water changes. Here is how I was taught:

-Do a 50% water change every 1-2 weeks and gravel vac at the same time
-Clean the canister 1-2 days after the water change (or vice versa...the stagger approach)
-Only use tank water to clean your media (sponges, etc.)
-Always use a de-chlorinator
-Lastly, always test your water parameters after the water change

This isn't complicated, but it could be for someone new to the hobby and could be causing fish stress and fish loss.

Thoughts?


By the way, I agree with all of you.
 
on a side note:

I only have 2 female bettas in my 75g tank and every time I do a gravel vac there is a bunch of detritus / organic matter that I pick up. How can two small fish produce so much waste in one week? Am I missing something?
 
Regular water changes won't kill fish. Its leaving the water unchanged for months and then doing a change or big clean-up that kills them. This is for one of two reasons:
  1. Disturbing the accumulated muck brings it into the water column and poisons the fish
  2. The tank's chemistry changes over time. Eventually the pH drops and the tank gradually becomes more acidic due to natural processes. When you add fresh water this can cause a large pH swing which can kill fish.
Clean fresh water never killed a fish - its the other factors. The best way to avoid this is to do regular substantial changes as that keeps the chemistry stable. If you inherit a badly neglected tank it makes sense to change 10% of the water every day for 2 weeks so that the chemistry normalises slowly and you don't shock the fish. And if you are going to disturb the substrate move the fish out while you do it.

Aside from this one exception large changes are always better than small ones. If you remove 25% of the water it means you leave 75% of the bad stuff behind. I have 3 tanks and regularly change 75% per week. I have never yet had a fish (or shrimp) die because of this. TBH since I have been following this routine the only fish I have lost have been due to old age.
 
on a side note:

I only have 2 female bettas in my 75g tank and every time I do a gravel vac there is a bunch of detritus / organic matter that I pick up. How can two small fish produce so much waste in one week? Am I missing something?

I have a 10g tank with plants and snails but no fish; it is my QT for new fish so I keep it running permanently. I do water changs less often than weekly, maybe every three weeks, because there are no fish. The detritus is sometimes more than one would expect with zero fish, though the snails are obviously eating organic matter they find and breaking it down. Plants do shed dead leaf matter more than one might think.

There are organics in tap water, and that means in the aquarium various species of bacteria eating them. Even with no fish or no plants.
 
Another factor to consider is if you have a well planted tank with fast growing plants any spike in ammonia due to the water changes should be absorbed by the plants and the lost of the bacteria is not a real concern.
 
With a couple of reservations, I concur with what others have posted here. @Colin_T and @seangee are right on the mark [edit, as is @Retired Viking who posted wile I was typing this], but I will comment on the specifics raised in post #7 by @cupofjoel.

Do a 50% water change every 1-2 weeks and gravel vac at the same time

Partial water changes should be once a week [= "regular"] and they must be substantial. This can sometimes depend upon the fish load (involving not just numbers but species and behaviours, something many fail to realize) but the fact remains that even with only minimal fish, the more water changed the better the fish will be. We can never even begin to replicate the change-over of water in the fishes' habitats, so the more water changed the better. This leads into the "last" point so I'll respond to that...

Lastly, always test your water parameters after the water change

The more water changed, the more stable the parameters. This assumes the aquarium is biologically balanced to begin with, and not overstocked (too many fish, or too large fish, or non-compatible species combination...all of which impacts the biological system more). The parameters should be identical from week to week, permanently. The pH is a good indicator parameter (GH and KH are less likely to be significantly fluctuating, but that's another issue entirely), and if you test the tank water prior to the water change, and the pH is always the exact same or only one or two decimal places different--that is a stable biological system. I ran tests of pH on my tanks for a couple years, for several months always prior to the water change, a day or two after, and then less regular, for 2-3 years. Each tank had its own pH, but it never varied, never. That is what you want. Even though the tank pH is say 5, or another is 6.2, and the tap water is 7.0 or 7.2, the pH never varies from week to week; the water change raises it by maybe two or three decimal points, but only for a couple hours.

Nitrate, not a parameter technically but a condition, is another important test. Here again, it should never go up between water changes; if it does, there is something wrong. A stable biological system involves biological and chemistry factors that being in sync will maintain a stable system and it will respond properly to any adversity (within reason) and deal with it.

Clean the canister 1-2 days after the water change (or vice versa...the stagger approach)

I used to do this with my canister filter tanks, but more out of saving energy than real need. When I had my house with a fishroom of 8+ tanks, including the 115g, 90g and 70g, it took three hours to do the water changes alone. No problem with that, but spending an hour to properly clean the canister (including the filter hoses and media) was a lot, and this task was done later in the week and I usually did the three large tank canisters at once to avoid more mess.

The aim is to have a biological system that is stable without the filter running. The filter in my tanks is only there to move water, to provide currents either for fish, or to ensure a good surface exchange of oxygen/CO2. I never rely upon them for biological filtration. If the tank depends upon the filter for this, it is more likely not in balance to begin with. However, I do have live plants, and every tank has a good cover of floating plants, and no filter will ever equal these unless the tank is biologically imbalanced to start with.

Only use tank water to clean your media (sponges, etc.)

I have never done this, in more than 30 years of fish keeping. Same principle as above...if the tank depends upon the filter, there is likely something wrong. And if the tank can function biologically without the filter, then it does not matter whether you kill nitrifying bacteria or not. But the other thing is, that chlorine alone is not likely to kill this bacteria; chloramine might, I have not looked into that. I recall a marine biologist teelling me a few years ago that she always advises new tank owners to use tank water for the first few months, out of caution because they are less likely to recognize things, but after that, waste of effort. And here again, floating plants make this all completely irrelevant; the amount of ammonia/ammonium that floating plants can take up is considerable; Tom Barr once mentioned to me that it would be virtually impossible to overload an established planted tank with too many fish to ever cause ammonia to rise above zero. Within reason obviously.
 
thanks everyone, I really love this community.

I will take everything said and adjust my maintenance. Sometimes i want to go back to a bare bottom tank.
 
I do 50-75% water changes once a week. I clean my filters once a month, on a water change day. No issues. I rinse my media in tank water, though every now and then I will rinse my sponges in tap water. And I can't even remember the last time I tested my water. When I did used to test, I would always get 0, 0, 5-10. Consistent, large water changes have helped me avoid many of the issues that I see on forums.
 
I also do 50% weekly and one big 75%+ monthly to flush out the system. It is a good habit to get into but for me it is a lot of work lugging around RO water jugs to mix with my dechlorinated tap water:good:
 

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