Please Help;they're All Dying!

[zack]

65 gallon tank
12(and decreasing) corys
1 angel
multiple tetras
1 synodontus eupterus
1 upsidedown cat
well planted, well aerated and filtered tank. 2 strong airstones in each backcorner and a hot magnum 250 (gph) hang-on-the back filter. seachem fluorite, sand and river gravel about 2 inches deep for the substrate.
temp 80-82 ph 7.5, 0 nitrate and 0 ammonia. tank has been going for more than a year.
i do feed live tubifex worms every 3-5 days and maybe a parasite has been introduced. i see nothing at all on any of the fish.
THE PROBLEM
over the last few weeks i am losing fish. mostly fish which live at or near the bottom. most have had no visible signs of a problem. and just the day b4, looked fine. i have a brochis splendins now lying on its side in a floating breeder tank. it had floated to the surface like two aeneus corys i found today which had died. it has large red blotches on its belly and smaller ones at the base of the fins. its eyes are a bit bugged out. i am sure it is too late.
most of the corys in the tank have no barbels. none. and their tails are a bit shorter than should be. maybe finrot but no red borders. just a disappearance of the tail fins.
am treating with melafix now and will see in the morning. but i am sure b. splendins will be dead. i've lost probably 7-8 corys, 1 flying fox, 1 bolivian ram and 1 killifish of some sort over this 3 weeks.
the fish all act perfectly normal up until the 'day of death' and they die looking picture perfect.
i am doing nothing differently from the past 30+ years of fishkeeping.
god this is getting long but, i hate watching them die. any help is greatly appreciated.
zack

 

[steelhealr]

Hmmm....tubifex....many references cite how they carry diseases..yet, some people feed them forever without any problems. Could there be anything new in your tap? Any chemicals in the house? Are you doing water changes? SH

 

[Inchworm]

Hi zack

Your corys are suffering from an advanced stage of a bacterial infection of some sort, there's no doubt about that. MelaFix is a mild antibacterial agent, but will not help at this point. Right now I suggest doing a big water change and bottom cleaning and adding an antibiotic such as Tetracycline or Kanamycin. You could also try Furan-2 or Maracyne 1 AND 2. If you live in the UK and cannot get antibiotics, you might want to try Waterlife's Myxazin or Interpet's Anti-Finrot and Fungus Medicine.

When using these medications, it's important to follow the full course of treatment, even if they have shown improvement. You can repeat the treatment if necessary, at that time, or move on and try another, but do not stop too soon. There are many different strains of bacteria that can cause the problem and some might be resistant to one medicine. It's also possible that your fish have developed a secondary infection too.

I would also suggest slowly lowering the temperature to no higher than 75 degrees F. to slow down the reproduction of the bacteria.

Now, it's also important to figure out the cause of the problem and eliminate it. What kind of corys do you have?

It's possible that your tubifex worms could have caused the problem, but this doesn't happen too often. I would consider the other possibilities too.

There will always be some harmful bacteria in a tank, but corys don't become infected until something causes enough stress to weaken their immune systems. These stresses can include, but are not limited to, such things as aggressive tankmates, overcrowding, overfeeding, temperature fluctuations especially sudden increases in temperature, elevated nitrite or nitrate levels, low oxygen content in the water, infrequent of inadequate water changes.

Your deep substrate is something to consider too. Could it be emitting poisonous gases? If so, the bottom dwellers would be the first to be effected by it.

I hope this helps and that your corys get well quickly.

 

[zack]

well thanx much lil young fish lady and steelhealr! nothing new in the tap water i suspect. no chemicals in the house are used. some incense at times though i dont think that is a problem. last week i did about a 65% water change. vacuumed down to the bottom glass in places i wouldnt destroy the plants. not much of anything came up out of the substrate. since it poured last night, i added about 8 gallons of rainwater to the tank this morning. i live in florida so i can try the other meds you have mentioned. two weeks ago i tried a dose of paraguard for a week. seemed to be effective but now the probs have returned. it would be hard to get the temp down to 75 due to the heat but i will see what i can do. i thought heat killed the bacteria?
i have 3 albinos, 3 sterbae, 3 bronze, 3 metae, 1 paleatus(which has not grown more than 1/4 inch since i've had it for more than a year! i suspect a genetal digestive tract defect) and the b splendens did die last night. i also have 5 otos and the 5" syn. eupterus and a 3" syn. upside down cat.
nothing that i witness bullies the corys. maybe the eupterus at night, but it has been in there for months now. another bit of data is that for months and months now many of the botom dwellers scrape/flash on a regular basis. even my african knife does this. the paraguard has stopped this by about 90% but now they just die.
no temp fluctuations. the parameters always stable.
the depth of the substrate is a question i have too. about 8-9 months ago i scooped out about 5 large quart-sized cups of gravel. maybe i need to do more???
which would you use first, kanamycin or the tetracyclene? would either affect the plants?
thanx for all your help.