Scummy tank: Partial or 100% water change?

[Jim Sinclair]

I was on holiday for a few days. Last water change was Friday. All tanks and the pond are getting water changes tonight. All but one of them seem fine. The exception had its filter intake get clogged at some point. It had cloudy scummy water, bad smell, one dead fish and one nearly dead but now reviving amazingly well in a hospital tank with 100% new water fresh from the tap (with Prime and salt added).

Meanwhile I did a 40% water change in the scummy tank, scooped as much detritus as I could from the tank floor, unclogged the filter, swooshed the filter media, and put in fresh charcoal.

The water now looks even more filthy!

Should I put all the fish into the hospital tank and do a 100% water change in their home tank? Or just wait and let the filter do its work?

I hope someone is awake to respond at this hour. I'm going to proceed with the routine water change of the one tank I haven't done yet, and then if this tank still looks this mucky, I'll probably go ahead and pull out the fish and completely drain and refill it.

 

[Colin_T]

Do a 75% water change, gravel clean the substrate, increase aeration and get the filter going, which you have already done. Then let the fish recover while the filter does its job.

If the water still looks and smells bad tomorrow, do another 75% water change.

 

[Jim Sinclair]

Let the fish recover in their home tank while the filter does its job? Or let them recover in the hospital tank (which doesn't have a filter and is much too small for this many goldfish)?

I think the culprit for the post-water-change cloudiness was charcoal dust. I don't remember if I swished the charcoal bag after refilling it (it's 4:30 a.m. here and I've been awake for about 22 hours), but if I did, I obviously did not swish it enough. I just took it out and swished it in a bucket of the cloudy water that I was getting ready to dump, and the cloudy water became even more cloudy.

Charcoal bag has now been swished and swished and swished some more. Most of the cloudy water has been dumped. I'm getting ready to refill with clean water. The fish are swimming around in the hospital tank waiting to go back home. The one that I thought was dead a couple of hours ago, that was floating motionless on its side just weakly twitching its gills, is now behaving completely normally. Can you guess which one it was?

This state of sleep deprivation is not a good time to be doing water changes and trying to figure out how to unclog filters and solve unexpected problems. But if I had gone to bed and left the water changes for morning, as I thought of doing but fortunately decided against, I'm sure that one fish that was almost dead when I found it would be dead by now, and by morning probably more would be as well.

Do a 75% water change, gravel clean the substrate, increase aeration and get the filter going, which you have already done. Then let the fish recover while the filter does its job.

If the water still looks and smells bad tomorrow, do another 75% water change.

 

[Jim Sinclair]

Water looks better this time after I turned the filter back on, so I put the fish back in. Here's the first one going home, after surviving a near-death experience and being the first one taken out:

 

[Colin_T]

leave them in the tank they are in.

 

[Jim Sinclair]

leave them in the tank they are in.

Too late. I already put them back. 19 goldfish in four gallons of water without a filter is not viable for very long.

I've just checked on them. They're a little more subdued than the fish in the other tanks, but they're all right side up and not floating at the top.

Almost 7 a.m. I have now been up for more than 24 hours straight. I'm going to take a nap.

 

[Jim Sinclair]

I slept until almost noon. All fish in all tanks (plus pond) were alive and active when I checked on them. The tank that had the clogged filter is just a little cloudy, but the declogged filter is running well and the fish seem fine, including the one that nearly died last night. Makes me wonder: If I had caught the problem just a few minutes earlier, if that tank had been the first one I did a water change on instead of the fifth, would I have been able to save the other one that really was dead by the time I got to them?

Anyway, thanks for helping my exhausted brain stay somewhat focused last night.