Kuhli loaches dying

[ScareCrow]

Hi All,
Apologies for the essay, trying to cover everything to avoid basic questions.
In the last week I've lost two kuhli loaches and just noticed another showing the same symptoms.
They appear to be struggling to swim, they'll swim upwards then drop back down landing however and where ever they fall (on their side/upside down etc). Ragged fins but no sign of fin rot. Other than that, physically they appear absolutely fine.
The tank is 100l and has been setup for a year. I carry out a 50% rainwater water change every week and clean the filter and hoses approximately every 8 weeks using rainwater.
The filter is rated at 800lph and distributed via a spray bar. Temperature is set to 24c and controlled by ink bird temp monitor.
The tank TDS is generally 60ppm after a water change and 80ppm by the end of the week. No idea of ammonia, nitrite or nitrate but I don't dose ferts at the moment and have lots of salvinia plus two large peace lilies growing out of the tank.
The water I do the water changes with is 30-35ppm, GH5 Kh4 (same in the tank), pH 6.5-7.
The tank is heavily planted with needle leaf java fern and bucephalandra, so plenty of hiding places.
Stocking is 6 corydoras duplicareus, 6 Sterbai, 6 kuhli loaches, 1 female kribensis and 4 juvenile sparkling gouramis.
For dry food I feed a mix of Dr Bassleer garlic, acia, regular, chlorella, fluvial bug bites colour enhancing, TA aquaculture blend and astax granules. Live food I feed grindal, banana and white worms. I normally feed once a day, sometimes every other.
I'm at a bit of a loss as to what is causing these deaths. As I write this the duplicareus are spawning and I use the same water/maintenance/feeding schedule in other tanks with no problems to adults or fry. I got the kuhlis nearly fully grown just over 2 years ago but I don't think this is age related.
Thanks for reading, any suggestions welcome.

 

[PARAGUAY]

Seems a mystery as l think,(not kept any for years)they are quite long lived and temperature seems OK for them ,test for ammonia and nitrite might be idea esp. as they live at substrate level,do you reminralise your water ,possibly suffering because of lack of minerals,,lack of scales make them more vulnerable to water quality issues, maybe someone who keeps khulis can give a little input

 

[Conort2]

I wish I could help but it seems like you’re doing everything right. My kuhlis are my longest lived fish and have been through all sorts, they’re an extremely hardy fish so it really doesn’t make sense.

They may have a pathogen that is specific to them that doesn’t affect other fish. I had this once years ago with a bacterial infection that only seemed to affect plecos and nothing else. Have acquired any new stock that could’ve brought something in with them?

 

[ScareCrow]

Thanks for your replies both.
@PARAGUAY I take your point about remineralising, though with my GH5 and Kh4 I think things should be fairly stable. Unless I'm missing something? My understanding is that they come from very soft low TDS streams. They're part of the reason I moved over to using rainwater, as my tap water is terrible.

Have acquired any new stock that could’ve brought something in with them?

I have wondered about this. All the fish in the tank have come from private breeders with the exception of the kuhlis. I did get 6 peacock gobies from a local shop. They'd been bred by someone locally but I lost 2 of them while dripping them. I mentioned it to the shop and they agreed to replace them after checking my water. I went back to collect the replacements a couple of days later and there were hardly any remaining so I'm guessing there was something not quite right with them. In my tank they lasted 6 to 8 months. They grew well and put on weight but one by one became skinny and died. At the time I'd assumed it was conspecific aggression but I never saw them fight and it doesn't explain why the last one died.

I've added some alder cones but have lost another kuhli today. I'll try to get hold of some Esha 2000 tomorrow. I think I'm also going to add a UV steriliser (not in conjunction with the the Esha) as I'm paranoid about TB. I don't think it is TB as the kuhlis all have the same symptoms but I've been considering a UV for a while.

 

[tam]

I don't know that it's necessarily related as you aren't having issues elsewhere, but GH5 seems quite high if you are using rainwater and no remineralisation or ferts. Likewise for your ppm to be going up by a third in a week seems a lot if you aren't adding ferts. I'd be curious what is causing that.

I agree, it's not age - kuhli are long lived - a decade easily if happy.

I would test nitrate/ammonia too - I doubt that's the issue in an established/heavily planted tank, but ruling things out is probably going to be the process.

Trouble is diagnosing contagious diseases from observation isn't very easy.

 

[castle]

Sounds bacterial to me, maybe internal parasite. Strong indicator is fin damage that isn’t healing. Fin rot can look different on any fish, but it’s quite common to have fin rot with other infections 👍

Rare to have TB without signs of an open would - as I understand it anyway.

 

[Conort2]

I think I'm also going to add a UV steriliser

These are really big in the marine side of the hobby, they swear by them. It’s something I always think about and then I spend my money on something else. It can Supposedly help with the spread of TB.

 

[Bradders]

Fish TB is likely to reveal itself in terms of weight loss, ulcerations and deformities over time (or one and not the other). But swimming issues can occur in rare cases. Really hard to tell.

I have had UVs before (on and off!) and think they are good, but only part of the solution. i.e. if your main filtration is lacking then they are a good idea to support.