Ammonia is 0
I’ve had the clown loaches for years. I don’t have a clue what to do next to try and save them. If I don’t try, they are just killing themselves. Anyone at all experienced something like this? I can’t film it as they are so fast you can’t catch anything when they are freaking out until they finally give up and fall to the floor injured, completely exhausted or knocked out.
I’ll give everything a try to save them….
Isn’t doing that many water changes a little bad for the tank and the fish?
I clean my tank every week, one week do the substrate with a gravel sucker. The next week clean the filter in the water I’ve taken out of the tank before I throw it away. All my equipment, buckets, nets etc aren’t used for anything but my tank!
Lights-wise are turned up around the same time and that’s after the sun has rose outside so it’s not a straight change from black to light plus normally they are hiding in the pipe or in the corner where the light doesn’t hang across.
No matter where I look, I can’t seem to find a trigger for the sudden change in behaviour. Every other fish in the tank isn’t showing any signs or stress or illness
My suspicion is contamination of some sort as well. The behaviour sounds very much like fish dying from being exposed to something that is toxic to them - like an ammonia spike, or if something deeply irritating to their skin/gills/etc has contaminated the tank, like bleach, hand sanitiser, or air freshener being sprayed in the same room as the tank;
something is getting to these fish and driving them into a panic since they can't escape the pain/irritation. I can see why you thought it may be a parasite of some kind, I'd suspect that too.
I also think the neons in the photo look washed out and pale, and is that a gourami hiding near the substrate? Those things also make me concerned about the chances of something in the water is affecting them all, and just hitting the loaches hardest since scale-less and more sensitive.
Sounds like you do the right things when it comes to their equipment/filter etc, so other things to explore - where are the fish buckets etc stored? Are the other tanks in a different room? Could someone in the house be spraying a cleaner or air freshener anywhere in that room? A plug in air freshener? What has changed in that tank or in that room recently? Anyone else ever put their hands in the tank or feed the fish? Is your food perhaps old and expired? Fish oils can be nasty once they go rancid, and the foods don't keep forever.
These are questions for you to ask yourself to see if something may have happened BTW, not demanding you answer them to me!
The tank - any decor that could be leaching paint chemicals or similar into the water? There are lots of things that can contaminate water that we cannot test for. I would also remove some of the large ornaments, especially any that are either new and a potential source of toxins, or anything that's old and looks as though it might be crumbling or flaky. The decor is for you rather than the fish anyway, and anything suspicious needs ruling out at this stage. I'd also go and get a big bunch of fast growing stem plants like elodea/water wisteria/hornwort, some ones like that to replace the ornaments, and hopefully help improve and filter whatever water quality issues (whether that's ammonia/nitrates/a potential contaminant) or not.
Yes, in the long term, the tank won't be large enough for their lifetime, the water softness/hardness issue should be resolved - but now is not the time. The size of the tank in comparision to the size of the clowns right now isn't causing this reaction or the deaths, so let's focus on the emergency first, eh guys? No point fretting about if the fish would need a new home or larger tank in a year or two, if they continue to die at this rate.
Lastly, do you have a quarantine tank? If you have one clown that is showing the same behaviours now, I would personally want to move him to an isolated quarantine tank or temporary set up to see whether he improves that way. But I would not move him to one of your other, main tanks with other fish, for fear of spreading the issue. Can talk you through how to make a temp quarantine using a plastic storage tote if you don't have a QT.