From: howardr@col.hp.com (Howard Rebel)
Newsgroups: rec.aquaria
Subject: Re: Tank Mysteries
Date: 31 Dec 1992 19:01:54 GMT
Organization: HP Colorado Springs Division
NNTP-Posting-Host: hplsdum.col.hp.com

rg@kunikpok.UUCP (R.G. Keen) writes:
> 3 tanks, freshwater, all stable for a couple of months.  Left tanks
> in care over the holiday. We cleaned them before we left, checked Ph
> & ammonia, did a periodic water change. Neighbor competent, no fish-
> keeper, not a fool either. all the fish in one tank were found dead
> the day after we left town, except the kuhli loach...about 28 hours 
> after we left them alive and well. Both other tanks were fine.  The 
> death tank had a high ammonia level but Ph was 6.2 when we returned
> after a week. The kuhli recovered after the neighbor put him in another
> tank. All the dead fish were bloated.  What killed them? 
> 
> think two things are possible - either the neighbor poisoned them :^)
> or something about the cleaning and water change did them in.

The cleaning might have done it; or several other things.

> [specs about water preparation for the water change, quite thorough &
> seemingly correct--same water was also used for other two tanks]
> I don't think the water did it.

Small chance, if your city water supply comes from more than one source.
Locally here, they use both resevoir & wells; with wildly different Ph,
hardness, etc.

> One expert says that a dead spot in the filter under a rock might have
> caused a collection of H2S which we released in the cleaning, & this
> may have poisoned the fish. 

Very probable, if one only uses UGF (under gravel filters) only in a
tank.  

> We did a relatively thorough cleaning

Really disturbed the gravel bed, made the water murky enough you couldn't
see anything in the tank?  

> and had to return part of the siphoned water to the tank to 
> avoid changing more than 1/4 of the tank. Any ideas???????

That also didn't help, especially if you made the water extra murky.
Stirring up a UGF once it's well established causes problems.

If you only made a hash of the one tank while doing the water changes,
an alternative would be to use a little water from another changed tank
(not highly recommended); or grit teeth & change more water than one
originally planned on.

Putting back visibly dirty water has never had good results....

The other reason (maybe) for the ammonia spike is that the gravel was
messed up too much & the bacterial 'bed' was disturbed--that will cause
everything to have to start all over again, filter wise.

Ammonia is one of the fastest things to kill fish....

P.S.  We've also found an UGF to be a time bomb waiting to happen; once
one hits about a year; even with regular gravel siphoning.  You might
want to consider another form of filtration for long-haul fishkeeping. 

> Mystery #2: One of our tanks has a mat of fungus, whitish gooey 
> threadlike mats in the top 1/2 to 1/4" of the gravel bed. The fish are 
> OK, and the water tests normal, but it's hard to clean since the mats 
> have to be broken up. What is this stuff, and what sin did I commit to 
> have it visited upon me????
> 
> Many thanks for any information. 

Dunno.  Are you overfeeding?  

[Disclaimer: everything above is the ravings of only one person, who's
 lost enough fish to mystery plagues....Howard's Wife Deb]
-- 
Howard Rebel hpcsos.col.hp.com