Columnaris?

[Kelpar32]

Hello. I've been reading these forums for years getting advice while dabbling in aquarium-owning, but have just now gotten around to joining, particularly because I have a relatively new tank which seems to be having issues I can't figure out.

It's a 15 gallon tank which has been fully cycled for about 2 months, and I'm hoping for it to become a nice, small, community aquarium (guppies, mollies, etc...) but stocking it has just been a disaster. I have fish dying left and right with almost no visible symptoms.

Over the course of a few weeks I stocked it with 3 corys, a small school of neon tetras, a platy, a molly, and 2 cobra guppies. Things went horribly. Some of the fish died suddenly after seeming healthy and others only showed generic signs of stress (lethargic, slightly clamped fins, hanging out near the top or bottom). Some of them died within the first 24 hours of having them and others within the first week or two. Finally a few days ago the guppy and molly showed symptoms of fin rot before quickly dying (the guppy's tail disintegrated and he lost all of his color in a matter of hours, the Molly died overnight and when I found it in the morning the only remains were a pile of white fungus). The survivors in the tank are 2 corys, 1 guppy, and 3 tetras- all of which appear quite healthy.

I've been diligently testing the water with an API kit to try and notice anything that may have been causing the problems, but everything is totally stable. I do have a high pH, but that is very normal for this area and it hasn't fluctuated.

Ammonia: 0 Nitrites: 0 Nitrates: 10 pH: 8.2

My only guess at this point is that most of the fish died from a strain of columnaris, and I've seen all sorts of conflicting information regarding treatment. For the time being I have added some salt to the tank (only a little, so that I don't overwhelm the catfish) but I'm wondering what to do next. Should I treat the whole main tank with antibiotics and risk ruining the cycle? Should I order kanacyn online and treat the seemingly healthy fish as a preventative measure? Is it even columnaris? And, when would you suggest I try adding a new fish in there (I'm eager to get some more, but very wary because I don't want to see any more fish die if my tank is the cause)

Sorry for the long post- I really appreciate the help

--
15 gallon tank and heater, Whisper EX 20 filter, Whisper 20 air pump (recently added)

Stocked with:
2 Julii Corys
3 Neon Tetras
1 Cobra guppy

 

[johnny leftist]

If it was columnaris you would know. The fish would develop patches of white fuzzy fungus growth on their bodies or in their mouths. Are there any store-bought decorations inyour tank? A lot of cheaply made ornaments have metal struts or wires in them and this sounds like something supersystemic like a heavy metal toxicity in the water. Either that or your water supply has a LOT of chlorine in it and you're not using enough conditioner.

 

[Kelpar32]

I do have pretty typical petco bought decorations in the tank. A few silk plants, a no-fishing sign (perhaps the paint on that could be the issue?) and a fake log for the fish to swim through and hide in.

The tank is being run on well-water so it shouldn't have chlorine in it (I still use Prime for all water changes), but we've always suspected the water may have a high sulfur content. Would that cause this sort of stress/symptoms on the fish? And would increasing the de-chlorinator reduce that, or would I need to switch to bottled water of some kind?

 

[Kelpar32]

I'm not sure if it's relevant, but within the last week or two there has also been a bloom of brown algae in the tank. Not a huge amount, but it did start becoming noticeable around the same time I started losing fish.

 

[johnny leftist]

Brown algae can be a sign of increased sulfur if you were already suspecting it was in your water. You may want to switch to bottled or prefiltered (like with a brita pitcher) and see if that helps. If you have fish that prefer harder water you may need some calcium tabs to get it within their comfort zone since purified water has no minerals at all.

 

[Kelpar32]

Hm, okay, thanks for the advice. All of the current fish still seem healthy, so maybe they have just adapted to the water/are strong enough to handle it. I'll start gradually switching over to bottled water and see if new fish handle that better. Thanks for the help!