How long to leave tank empty after disease outbreak

[svelez]

Hi everyone,

It's been a frustrating few months, and unfortunately I threw in the towel and euthanized my remaining rasboras (a mix of chilis, phoenix, and dwarf spotted). I ordered them back in March/April from a store I've previously gotten very healthy fish from, but just after a week of having them, they started dying off one by one. After trying every med under the sun (that I could get my hands on anyways), and still losing them 2 or 3 at a time, I gave up. 

I suspect the main issue was some sort of parasite. Symptoms included heavy breathing/gasping at surface and bloat. Some would just turn pale and hide near the bottom of the tank before expiring. Many of them would start with an area on them with a white cast (not solid white; it would change depending on angle and lighting) that would get worse and worse. I suspect heavy mucous production? Often, when I dosed a parasite med (I tried prazipro, paracleanse, and Ich-x), at least one fish would end up with a bacterial infection afterwards. I suspect maybe from parasites dropping off and leaving open wounds? Anyways, the bacterial infections looked suspiciously like columnaris, so I also treated for that. I tried Maracyn 2, and then when that failed, the Kanaplex/Jungle Fungus Fizz tabs, and when that also failed, I tried level 3 salt treatment for 2 weeks!!! Nothing worked, and the bacterial infections (which were the classic saddleback shaped white patches) would just continue to spread and eventually I would just euthanize the poor fish.

Now that all the fish are gone, I'm considering leaving the quarantine tank running empty for a while; it is a quarantine tank that I actually have running always with some plants and snails to keep it cycled in between new acquisitions. I am hesitant to tear it down because I have nowhere to rehome those plants and snails without potentially introducing something nasty into my display tanks.

I've seen online that columnaris would need about 36 days to die out in a tank (or die back, since it may always be present). And parasites like costia can form cysts and just "hibernate." If I want to let the tank go fallow and leave it running with just plants and snails, how long am I looking at? A few months? Or longer? Or should I tear it down and leave it dry for a few months? Not sure the best course of action as I'm finding conflicting info online about some of these parasite's life cycles.

Thank you for any suggestions!

Edited June 30 by svelez

[gardenman]

I had a similar issue many years ago. I'd bought a small koi at a very good price. It brought something with it that killed every fish it came into contact with, but the koi itself was immune from whatever it carried. I went through the whole array of antiparasitic drugs and they'd help the symptoms, but then the fish would nosedive after the treatment ended and die. I ended up draining and parking all of the involved tanks and supplies (filters, nets, etc.) for a year or so before I got up the courage to try again. No problems after that.

I'd recommend removing the plants and putting them in a standby container of some sort.  Then boiling the substrate and bleaching the tank. Replant the plants and hope for the best. Put in a sacrificial fish or two to see if the problem recurs. 

[Tlindsey]

On 6/30/2024 at 8:51 AM, svelez said:

columnaris would need about 36 days to die out in a tank (or die back, since it may always be present). And parasites like costia can form cysts and just "hibernate." If I want to let the tank go fallow and leave it running with just plants and snails, how long am I looking at? A few months? Or longer? Or should I tear it down and leave it dry for a few months? Not sure the best course.

I personally would empty the aquarium and fill aquarium with 1pt chlorine bleach and water let sit a day or two. Also would toss the ornaments in the aquarium as well. If HOB filter clean with bleach and water.  Substrate filter media and biomedia tossed. @svelez

 

[svelez]

Thank you for the replies! Any suggestions for what to do with the snails? Bladder and ramshorn I don't really care, but I have 4 mystery snails that I'm not sure what to do with during this process. Plus I don't know if they could be carriers/in-between hosts, so can't move them to another tank with fish, obviously.

[Markp2483]

I think you could leave the qt tank setup. I would remove the substrate. Probably best not to have substrate in a qt tank if possible easier to see fish poop and vacuum.  Wash plants, snails and tank in fresh water a couple of times. Reassemble add a UV sterilizer if you have one handy. UV sterilizers are great to have in a qt tank just don’t use it at the same time as meds.

[svelez]

I do have a UV sterilizer! Thank you for the advice 🙂