Major Water changes - Leave fish? or not to leave fish?

[Redhawk]

Hello again,

Not sure if I'm just terrible at keeping fish or just have very bad luck.  I did some major gravel vaccuming this past weekend on my 20Gallon High tank which was homing a male betta and a couple of corys.  While I had not done such a major water change in the past I didn't plan on it being a 100% water change so I did not take the fish out of the tank and kept the water level around 30% at the lowest for a very short peroid of time.  (Less than half an hour)

All good right?  Well.. one of my corys got stressed out with all the movement and ended up passing away on Sunday.  I haven't had them long but he defiently seemed fine prior to the water change.  I immediately tested my water multiple times and everything was within reason.  I have very hard water but PH was 7.4 (ish) again, not great but not terrible, No Nitrates or Nitrites, and no Amonia was detected.  

Further investigation and research led me to one of the videos by Cory on AquariumCo-Op that mentioned that corydoras have a certain type of toxin that can get released when stressed out that can kill other corydoras.  While I'm still a little skeptical on this being the fault it brought me to the bigger question.  When doing a major water change, greater than 50% we'll say for example, what is the proper etiquite for handling the fish in the tank?  Do you take them out?  Do you leave them in?  Are there any special precautions that you take to help reduce their stress?

[Guppysnail]

There are different thoughts on doing water changes over 50%. I read somewhere that studies were done on it disrupting the natural biome in a planted planted tank far to much. (Possibly @modified lung mentioned it)
I don’t recommend greater than 50%. 

Netting fish will stress them far more than gravel vac and water change. 
 

I recommend gravel vac more often, maybe not as thorough but enough they are used to you doing it so they do not freak out. If you find yourself in a situation where you are removing to much water and are not finished add water and wait a bit to finish so they don’t freak out as much. 

Edited November 21, 2022 by Guppysnail

[JettsPapa]

I agree with @Guppysnail.  If just the stress of the water change killed the fish it would likely have also died from being netted and put into a different container, then netted out of it and put back.

[TOtrees]

I think something we don't appreciate enough is the cumulate nature of stressors. What I mean is that I doubt the water change itself is what caused problems. Fish can tolerate quite a few stressors at a time, whether they be ammonia, nitrates, pH, temperature, light, and so on. That's to say nothing of the intangibles like the age of a tank (not seasoned, in cory's vernacular) or competition or imperfect diet. If a few of the above aren't "ideal" that's not a huge deal, assuming the fish are healthy to start with, and assuming the departure(s) from "ideal" aren't massive. But a lot of small stressors, or a few bigger ones, make an additional disturbance, such as the behavioral stress of a big vac plus a ton of mulm and detritus getting kicked up and possibly affecting water chemistry, more significant. 

I would suggest that either the new water you added was too different from the tank water, the dechlorinator wasn't properly dosed, or something was going on before you ever did the change and the change pushed a few over the edge, so to speak. 

I will say this: if you're doing the water change right, no amount of water change should require the fish to be removed while you do it. I've seen vids of tropical breeders with tanks that can exchange like 95% of the water in just a few seconds. It's like a fire hose 😮 Water drains through big bulkheads, and comes back in at high pressure. Granted, these are bare tanks with just the fish in them, so there's no disturbance to substrate or whatever. But the key is that the new water is basically identical to the old water, just minus some metabolism by-products. 

My point continues to be that it's not the water change that causes problems, its the change in parameters or environment. Just because it doesn't appear on your test kit doesn't mean it's not there. 

My suggestions for moving forward:

- double check that you're dosing the dechlorinator right (feel free to post the brand and how you use it here for additional sets of eyes). 

- confirm that your water changes have the right temperature range. minor change in temp is fine, but more than 5F difference in tank temp from start to finish shouldn't occur. Not to say it's always bad, some of us intentionally do it to stimulate breeding or whatever, but here we're trying to control differences/variables. Ie if we know/confirm that the temp of the tank didn't change by more than 5F from before to after the water change (regardless of how big the change was), we can say that temp change wasn't the issue, and cross it off the list. 

- do not combine big volume changes with gravel vac, do these separately. For a reasonable once-a-month maintenance vac, you shouldn't need to remove more than 10-20% water volume. If you're vac'ing half the floor, and that lowers water by 50%, you need to go to vac school and improve your efficiency https://www.youtube.com/watch?v=CjNTUbUnwfY. Not trying to criticize, just confirming assumptions and trying to limit variables. 🙂 To put this into a different perspective, poop and mulm in the gravel won't kill your fish, but disturbing the poop and mulm too much might. 

- If you have so much detritus in the gravel that you need to do such major cleaning, might you be feeding too much? 

:) 

 

[Schuyler]

How do you add the water back? Do you pour it in our do you use a hose? If you poured it in maybe the force of the water and quick change of parameters combined to over stress?

How many corys do you have? Maybe rather than just replacing you get a few more so they can feel safer together

On 11/21/2022 at 7:33 AM, TOtrees said:

My suggestions for moving forward:

- double check that you're dosing the dechlorinator right (feel free to post the brand and how you use it here for additional sets of eyes). 

Is it possible to over dose dechlorinator? I know it uses up oxygen to do it's thing but I normally squirt some in the bucket before filling so that is highly aerated for a while before going into the tank. I don't know if I have basic chlorine vs chloramine so I tend to do the higher dose and because I'm paranoid I add a little bit more just in case.

[TOtrees]

On 11/21/2022 at 10:57 AM, Schuyler said:

Is it possible to over dose dechlorinator?

I want to say not it's not possible to over-dose it, but there's always someone out there that's pushing the limits (always by accident or misunderstanding). Eg prime is 1mL per 10 gals, but another brand might be 10mLs per 10 gals. As with my temp discussion, I just think it's prudent to be able to cross as many possible problems off the list as possible. And in truth I was more thinking of underdosing not overdosing. 

[modified lung]

Big water changes are usually fine but they can definitely kill weak or otherwise stressed fish or fish that might have a mild illness but aren't showing any signs. I'm not completely sure why. It could be a microbiome change from the treated water which is my working theory or maybe it's an osmoregulatory thing. It happens even in multi-tank systems where water changes are done through the sump so the fish never go through the stress of a gravel vac or the water level in their tank lowering. 

On 11/21/2022 at 7:33 AM, TOtrees said:

I think something we don't appreciate enough is the cumulate nature of stressors.

Exactly this. The way toxicity studies look at one stressor at a time in a lab then report a number makes people think that number matters in the real world. It leads to a lot of bad advise saying "as long as you keep ammonia below whatever specific level..." If ammonia is your only stressor, then sure. But that's very unlikely.

[Odd Duck]

I’ve done 90% water changes and not lost fish.  Even did 100% water changes when a tank sprung a leak and I found my cories laying sideways on the foam matten substrate.  They got plopped directly into another 10 gallon tank and they went right on with life with not a single issue.  That tank likely had very similar parameters, though.  I’ve plopped Jack Dempsey fry directly from yucky, overcrowded tanks (I got very overrun with fry) directly into freshly mixed, dechlorinated water (I did agitate it for a good bit before filling bags) when I was bagging them to send to new owners.

Something else is likely stressing your fish to cause these problems, then the water change is a last straw.  When I had substrate that needed vacuuming, I always did no more than 1/2 the substrate at a time unless I was emptying the tank completely after moving all fish to a new tank, selling all fish in the tank, etc.

[Patrick_G]

It’s very common on the planted tank world to do 70% water changes once a week if you’re using the EI fertilizer dosing method. The same goes for Discus keeping or large scale breeding. 
 

I’m not saying that the water change didn’t lead to the death of your Cory, but it does seem like some of the best aquatic gardeners and the most productive breeders are doing large water changes and seeing benefits from them. 
 

[nabokovfan87]

On 11/21/2022 at 4:53 AM, Redhawk said:

Not sure if I'm just terrible at keeping fish or just have very bad luck.  I did some major gravel vaccuming this past weekend on my 20Gallon High tank which was homing a male betta and a couple of corys.  While I had not done such a major water change in the past I didn't plan on it being a 100% water change so I did not take the fish out of the tank and kept the water level around 30% at the lowest for a very short peroid of time.  (Less than half an hour)

All good right?  Well.. one of my corys got stressed out with all the movement and ended up passing away on Sunday.  I haven't had them long but he defiently seemed fine prior to the water change.  I immediately tested my water multiple times and everything was within reason.  I have very hard water but PH was 7.4 (ish) again, not great but not terrible, No Nitrates or Nitrites, and no Amonia was detected.  

Sometimes it happens.  Dropping the water level is always a stress for fish, but sometimes that's how you can even trigger breeding!  Alright, so I will start by saying, NO, you're not terrible.  There is a few things I do in WCs to keep things going and I am someone and I know many others who often do 60-80% WCs when you really need to clean out a tank.  It might not be every single time, probably best not to, but doing that every once in a while isn't a bad thing when you have an issue. 

Keep the water level above the dorsal fin of the fish so they can swim and get away, hopefully reducing stress and their tendencies to scrap or scare themselves getting away from hands / siphon.

I have an airstone I keep in most of my tanks specifically for WCs to keep things cycled and flowing.  I have had tanks sit for a lot longer than 30 minutes without issues.  Not a requirement, but it does help.  They will often crowd wherever flow is as a sort of "safe haven".

Whenever you're doing a big WC, double dose your dechlorinator just for the heck of it.  Pour a little extra, whatever you want to call it.  If you're vastly shifting parameters that's one cause for concern.  Temperature is another one, but the major thing is just there's a big shift of stuff and dechlorinator helps with that type of thing, heavy metals, etc.  For shrimp tanks this can be especially important.
 

On 11/21/2022 at 7:57 AM, Schuyler said:

Is it possible to over dose dechlorinator?

Generally 2x dose is very safe. 5-10x is "over dosing"  Depending which you have it should list it on the back.

On 11/21/2022 at 4:53 AM, Redhawk said:

Further investigation and research led me to one of the videos by Cory on AquariumCo-Op that mentioned that corydoras have a certain type of toxin that can get released when stressed out that can kill other corydoras.  While I'm still a little skeptical on this being the fault it brought me to the bigger question.  When doing a major water change, greater than 50% we'll say for example, what is the proper etiquite for handling the fish in the tank?  Do you take them out?  Do you leave them in?  Are there any special precautions that you take to help reduce their stress?

I genuinely doubt it's toxin release.  If this was the case you'd have a lot more dead fish.  You would see a white cloudy water and then you'd see fish dying withing 30 minutes or so.  There is a members talk specifically on this toxin and research.  I highly recommend it!

I think the fish was simply stressed and probably ran into something.  Or.... PH and temp played a role here.  It does happen, unfortunately.  Sometimes fish can take months to acclimate from old home to new home and your water might not be "perfect".  This isn't to say don't change water, but just try to test, match parameters and avoid "old tank" syndrome.  This can happen in new tanks, or from the perspective of the fish.... long term acclimation issues. 

Diseases might take weeks to show up.  Months even.  Always, consistency is key. 

 

[nabokovfan87]

Question.  What temp are you keeping them at?  What does your filtration look like on this tank?

ORD.  Awesome comments and conversation on this thread.  I really enjoyed reading through all the great advice.

[tolstoy21]

I haven't read what other have posted yet, but I'm firmly in the camp that as long as the water is similar in parameters and temperature, water changes should have little effect on the fish.

I move fish around my fish room a decent amount of time and I routinely move fish from an established tank to a new tank. By this, I mean tanks I set up that day and haven't cycled or anything.  Now, I do put in pre-seeded sponger filters and plants and driftwood that already is seasoned and have beneficial bacteria, but the water itself is hours old. I have yet to see a fish, or even shrimp, die in this scenario.  This would be the equivalent to a 100% water change from the fish's perspective.

I do a lot of auto-water changes and some of my tanks get maybe 50% every day. But the changes are gradual and periodic (on a schedule). I think I remember seeing saw a video where in Dan's Fish's new setup, all his fish are living in a scenario where their water is constantly being exchanged, like they are living in a river. 

When I change water manually, I just use a Python and pump it into the the aquarium, maybe doing 5 to 10 gallons in a few minutes.I try to keep the flow rate slow enough to not kick up all the mulm and annoy the inhabitants.  Sometimes I'll siphon water out first, other times I let the water flow out bulkheads at the back. Either way, there is little disruption to the fish other than fresh water.

As for vacuuming. I'm in tanks all the time, sucking stuff out. They really get used to me doing this and it doesn't bother them.

Now, where I do see fish die is when I'm in the tank, moving filters, moving driftwood, chasing fish with a net, putting them into a catch cup. Every now and then, the stress of this all is too much for some poor fish and later that day, or the next, I'll find that one died of stress.  In fact, I see a greater correlation between me disrupting a tank and deaths than I do from water changes where all I do is pump new water in and take old water out.

I will fully admit, this applies to fish and I have no experience on how this effects plants. 

 

Edited November 22, 2022 by tolstoy21

[tolstoy21]

On 11/21/2022 at 11:03 AM, TOtrees said:

I want to say not it's not possible to over-dose it

What if you exchange all the water with 100% de-chlorinator?  😛

 

Edited November 22, 2022 by tolstoy21

[Redhawk]

On 11/21/2022 at 5:18 PM, nabokovfan87 said:

Question.  What temp are you keeping them at?  What does your filtration look like on this tank?

ORD.  Awesome comments and conversation on this thread.  I really enjoyed reading through all the great advice.

For PH, I do my best to keep it as close to a 7 as possible.  Mind you if its a 7.2 i'm not going to add anything as I've been trying to make the minimum amount of changes to help the tank "do its thing" as its still in the early stages of cycling.

For temperature, I have my Betta which prefers high 70's, low 80's so I tend to meet on the middle to high on this.  Around 78 to 79 degrees.

As far as filtration, I am currently using a Medium sized aquarium co-op sponge filter.  I have my male Betta in this tank so my original HOB filter just had to much flow to keep it on this tank.  I have a Marineland Penguin 150 coming on Wednesday that I plan to throw on here to help with the mechanical filtration as recommended by someone on a different topic of this forum.  Might have to modify it a bit to help keep that flow from being to strong for my Betta's fins though.  Waiting to test it first.

You are 100% right on the advice.  I haven't had time to respond but I have read word for word every single reply on this thread and I can't express my gratitude enough for everyone's advice and stories.  While I'm here to find some answers for myself, I truly hope these comments and advice will also help the next person.

On 11/21/2022 at 10:33 AM, TOtrees said:

you need to go to vac school and improve your efficiency 

 

I couldn't help but chuckle at this but at the same time, your 100% right.  (About the efficiency)  Looking back, it was a bad move to do both at the same time and I obviously regret it now.  It absolutly could have been the difference in temperature or PH of the water coming back into the tank.  I'll have to keep a closer eye on that going forward or do my best to match them appropiately.

As far as water conditioner, I use this: https://www.petco.com/shop/en/petcostore/product/imagitarium-betta-water-conditioner

I've asked Petco the last time I was there if there was anything "specific" that made the water conditioner different for Bettas.  They gave me the typical saleperson answer.  "Well if it has Betta listed on it then it must be special"

I can't say I agree or disagree (With above Petco salesperson statement), but I am probably going to switch to something more popular like Fritz going forward.  Again, not to say it was or wasn't the declorinator.  It might have been working fine or maybe it needed more time to bind up the Chlorine and Chloramine.  Can't say for sure.

As everyone has mentioned, I am going to look for other signs of stress, and take a step back and look at the bigger picture for posible stressors and do my diligance to reduce them before making drastic changes such as major water changes.  

[jwcarlson]

I do darn near 100% water changes on my discus every evening (laying on side, having to kick around) and they do just fine.  I do large water changes (50%+) in my planted tanks as well, but do not vacuum the gravel.  Haven't had any issues.  The discus sure seem to like their changes, they are happy and eating during it. 

Edited November 22, 2022 by jwcarlson

[jwcarlson]

[LizLeFemme]

I usually leave my fish in. I did a 75% water change 2 days ago because I’ve been really sick and hadn’t been able to keep up on water changes for 2 weeks, All the fish are doing fine but I’m afraid I caused a bacteria bloom that is taking forever to clear up. Looks better today but I won’t do it that way again I don’t think.