Mystery illness

[Slappy Kincaid]

I have a 30 gal planted tank. My fish keep dying, one at a time for no apparent reason. I've had my water tested and everything is within normal parameters. The fish show no symptoms, just turn up dead about once a week. New fish are usually dead within 72 hours. I think it is bacterial, but I can't match it up with anything I can find online. Even if I don't add a new fish, established fish just randomly die once a week. I have a tank with mostly tetras, 2 mollies, a pleco, and 2 rasboras. I can't figure this out. Any suggestions on how to approach a mystery illness? I'm thinking of just burning the tank and starting over.

 

[Autumnsky]

A couple ideas...

Are you familiar with the nitrificaiton cycle? Article link in my signature explains the cycle, provides helps with some important basics and tips.

What are your water parameters?

You said good, but have you got any of the numbers for the things being tested?

Ammonia
NitrIte
NitrAte
pH

GH/ KH
TDS

So I am wondering about the tank and how long it has been running for?

And pH TDS.

Also when the water evaporates do you add more treated tap water into the tank. How many gallons do you figure you are adding each week?

How many gallons do you change and how often?

The other concern is wondering about Columnaris. There seem to be reports of a few versions of this disease which, kill lightning fast wiping out a tank in a couple/few days, a medium fish dies every couple /few days and the other which is and the last more like every week or so a fish dies.

Have you noticed any white/cream, gray patches on the fish? Fuzzy growth at mouth?

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Have you looked for any worms in any of the areas of the fish like eyes, gills, mouth, anus - black or white dots which may move?

What does the fishes poop look like and what are you feeding them?

 

[Slappy Kincaid]

I don't have specific parameters on the water, just that I've had it all tested by my buddies at the local fish room and found nothing elevated in nitrates, nitrites or ammonia. I feed them tetra flakes and an algae wafer (for the pleco) once every 2-3 days.

I replace evaporated water with R/O water from the aquarium supply store (my tap is really alkali--above 8.0). My pH is 7.46 in the tank. Tank is about 6 months old.

I haven't seen anything that looks like worms at all. The only symptom I've seen is one of my mollys has a yellow/brown spot on it's side. The dead fish look perfectly normal, just dead. Nothing odd about gills, no bloating or weight loss, no fungal spots or injuries. I don't even see odd behavior before they die--no agitated swimming or rubbing against rocks. Its so completely random.

The only common issue I've found is that bottom feeders die almost immediately--24 hours. Other fish deaths are in established fish and random. I've been talking to the guys at the aquarium shop and they're stumped as well.

One detail I didn't include is that I have an infestation of pond snails that were introduced with the first plants I put in the tank.

 

[Aiken Drum]

I wouldnt trust what a fish store says about water parameters unless they give you the numbers.

For instance, nitrates might be 0ppm and be within safe parameters, but 0 nitrate is a sign of an uncycled tank.

I would get the fish store to give you your water parameters or get your own test kit and test yourself.

There are regular posts on here where the fish store says the water parameters are good, but when the actual numbers come out, they really arent.

 

[Slappy Kincaid]

On my long list of things to get is a complete test kit, then.