Water change massacre.

[everussell]

Our 30 gallon tank had been doing fine for months and we would do partial water changes every few weeks with no problems because after we'd treated the tank for fungus on one of bottom feeders, the tank had a strange green tint that just wouldn't go away. Until the other day, when my boyfriend did a full water change, all of our fish and snails died. The last to go was a really huge bottom feeder who seemed to be doing all right after the massacre, and then stiffened up and eventually died, a few hours after everyone else.

What on Earth went wrong?! We think that the water may have not been oxygenated enough, or something, but that wouldn't really explain why the poor big guy died hours later.

 

[hey]

How many fish did you have in your tank?
how big were they?

 

[pl*co]

I have done a nearly full water change in the past to resolve problems and it resulted in more problems. That was when I was pretty new to the hobby. I think an important question would be, what were the readings of the water before and after the water change and over the days afterward?

The reason I ask, is that in my experience with my own tanks and even with small, partial water changes is, the PH will rise for a time. A full or even 50% water change will bring the PH way up (in my tanks) over the period of just one day. I also see this when I do a 1/3 change (I try not to do more than that). The only reason I'd do more than that at once is because I am impatient and haven't been diligent about water changes. Then I try to do too much at once, instead of two 25% changes over a period of days.

My point is, it is important to be careful when doing water changes. Depending the the issue, the smaller amount over a period of time beats all at once. In my opinion (and I'm the first to admit I'm not an expert... just a voice with some experiences), to do a full change is nearly the equivalent of starting a new tank, except you still have the biological thing going in the sand or gravel, as well as the filter, unless you changed that out too. You have to keep a close eye on the readings when faced with the need for a massive water change or it's too much of a shock to the fish. Sometimes it's tempting to "fix" the situation all at once, rather than over even a period of hours.

 

[amosf]

Could have been O2 or even just very different water parameters. And if you don't test the water before putting it in sometimes you can get caught with 'bad' water. I changed water once only to fill the tank full of nitrites and wipe out several fish. 100% water changes are always a touchy thing to do and really only something you do in an emergency - like when the nitrites were killing my guys I got some clean water and did a 80-90% change to save the rest... Hard to say what happened to ou without some test results

 

[SnakeIce]

I would seriously be looking into the condition of the water you have out of the tap. something may have been introduced to the water supply that was either to big a change and not overall detrimental or something I wouldn't want to ingest personally.

the first possibility would be something like they changed sources and the hardness/ph changed alot or they changed disinfectants to cloramines and you need a specific declorinator to deal with that.

if something bad got into your water it might be more than you could test for and I would be contacting your water supplyer or getting your water tested if it is a private supply.


or it could have just been the fish getting bigger, if they were in a to small a tank, and the stress of lack of room finally caught up with them and the first fish dieing started the dominoe effect of deteriorating water quality that killed the whole tank off.

 

[hey]

Correct me if I'm wrong, but it Could've been an ammonia spike. If you added the water straight from the tap and then dechlorinated, your beneficial bacteria couldve been severly depleted, and would not have been able to handle the spike in ammonia from putting the fish back in.

 

[pl*co]

"Correct me if I'm wrong, but it Could've been an ammonia spike." - Hey

Hey, good point. I completely forgot about that. It would have a faster and more potent impact than the PH would.

 

[qtaquaman]

Immune systems and fish

The green in your water was likely suspended algae so fine that it looks simply like green water. This plus only doing a water change every three weeks or so says to me your nitrates were high. But being high with three week water changes says to me your bioload is heavy, you mention large fish. I suspect your ammonia and nitrites were high as well, end result high nitrates=suspended algae. Your fishes immune systems were likely weak as a result of poor water over time and the 100% water change was too much of a difference,(consistency is important in the aquatic enviorment). The fish could't take the change and death was the end result.
Really the only time you can do such massive water changes is by either carefully matching the existing water parameters or better yet by doing frequent water changes, which in turn allow the fish to become strong and healthy there by allowing the fish to take a sudden change in the water chemistry and survive. :thud:

 

[RTR]

When you do sizable and frequent partials, the fish have no adaptation to do as the new water is very close to the tank water. In that case, providing that proper neutralization of the utility-added disinfectant is done and temperatures are matched, there is nothing happening to stress the fish.

It sounds like Old Tank Syndrome and/or chlorine/chloramie issues in this tank.

 

[TKOS]

I know that when my dad used to take care of our tank when I was a little kid he would do once a month total changes, including cleaning the whole tank out. This of course would end up with a lot of dead fish very quickly.

What exactly is your usual tank cleaning method versus what you did for the total water change?