Restocking after disease outbreak

[dent20]

I had a disease outbreak in my 125 last week that ended up killing several geos after they were placed in quarantine. Still not 100 percent sure what it was. Fish had clamped fins, some flashing. For those that died it was relatively quick. Most likely culprit was disease introduced by three new juvenile geos I added a couple of weeks ago, or a spike in my levels that I missed (was on vacation for a week and fish weren't fed, think I probably should have eased back into feeding schedules and water changes when I got back).

I still have three denison barbs and four cory cats in the 125 that are showing no signs of illness. I'm trying to decide how long to wait before re-stocking, ideally with new geos. I know the surest way is to tear everything down, but this is an established tank with plants, so I'm really reluctant to do that unless it's completely necessary. Any thoughts on how best to proceed/how long to wait?

 

[Drstrangelove]

Not exactly sure from the OP what happened:

1) did only the 3 new Geos die?
2) did only the 3 new Geos and some other (older) Geos die?
3) did all the Geos (new and old) die?
4) did all the Geos (new and old) and a couple of other fish die?

After just a week, I would wait and see what happens to the remaining fish unless someone can give you some certainty on what caused the deaths.

You could also do selective prophylactics and use various drugs and medicines. Not my favorite response to unidentified deaths, but that could be an alternative to more drastic methods like bleaching the tank.

 

[dent20]

No. 2. The other fish in the tank are still doing well, but the barbs did show some flashing in the beginning.

 

[duanes]

Some disease carrying pathogens can persist months after all fish have died, and return when new fish are added. A prime example is columnaris, it can sit dormant in detritus for months only to reappear once another fish is added.
Because other fish are now showing symptoms, I would't add anything else.
And if these fish die, breaking the tank down, and sanitizing everything may be your only reasonable recourse.
Otherwise you may be spending a lot of money on fish that die soon after being added

 

[dent20]

It's not columnaris. A couple of fish appeared to have ich toward the end, small white spots. Treated for that and it went away, but they still ended up dying in quarantine. I've never lost fish like that before though from an ich outbreak. Other geos from that tank did survive and are now in other tanks. Wouldn't say they're 100 percent, but they're doing much better. None of the remaining fish in the original tank have shown any signs of illness in about a week.