Unknown fish illness killing off fish, medications not working.

I have a 30 (115litre) precycled tank that's been running around 6months or so now. Its mostly a grow out tank for mollys and guppies but has 6 corys and a pleco. It gets a 50% wc and vacum weekly and levels are 0 ammonia 0nitrite and around 10ppm nitrates currently 5ppm due to amount of WC for medications.
Symptoms are strange, at first fish look dusty with a matte white sheen/cobweb It almost looks like velvet but is entirely white with no luminosity under light. They also flash/flicker uncomfortably on objects. Their scales can sometimes look 'bumpy' and tend to flake off to reveal a white crust underneath. No loss in appetite.
As symptoms progress (despite treatment) they end struggle to breath, spend time at the surface or trying to reach it, their gills are inflamed and their fins have pieces missing and look ragged. Just before they go they get the unmistakable 'red spots' on fins which indicate septicaemia and swollen eyes.
At the onset of symptoms I started treating for ich/velvet, using esha exit and then esha exit and 2000 combined, it seemed to get worse. Due to missing fins and gill inflamation I thought maybe this was because it was flukes. So i combined esha exit/2000 with esha gdex (prazinquantal) as directed and also hoped this would stop secondary infections, it continued to get worse.
I also tried flubendazole, as prazi was quite harsh on the fish and API whitespot/velvet. No improvements.
Its been well over a month but no medications seem to even show improvements despite completing 7 day treatments.
I even increased temps to 86(30c) to speed up the parasitic lifecycle...but this seemed to greatly make things worse and I lost a cory to a secondary bacterial infection. So i brought temps down to 82(28) to try to find a medium to kill whatever this is but not speed up secondary infections.
I live in the UK so access to medications is limited, any idea what this might be and whether its even curable?
The worst affected seem to be the corys (already lost 2) and my pleco (whom I may euthanise).

 

Perhapse a fungus?
You should probably fill out the sick fish form to streamline the information in your post next time.
It seems you have a pretty heavy bioload and might need to up your water changes. Look into a UV filter if you can.
I am a big fan of H2O2 to clean up the water column of single celled organisms and such. It's abundantly available and pretty simple to use. The general method is to remove your filter media, dose up to about 2ppm, let it run for about an hour, then replace your filter media. It will crash a cycle if used improperly, so do additional research before trying.

 

Sorry you have having such troubles.

Just to confirm,

• over the past 6 months there have been guppy and molly fry transferred from your other tanks as well as 6, now 4, cories, and a single pleco who is dire.
• What kind of cories?
• What is normal temp of tankÉ
• Are the fry getting this as well?
• Parameters are fine
• Treatment over the past month has been:
  • for ich/velvet, using esha exit and then esha exit and 2000 combined, it seemed to get worse.
  • for flukes: So i combined esha exit/2000 with esha gdex (prazinquantal) as directed and also hoped this would stop secondary infections, it continued to get worse.
  • flubendazole, as prazi was quite harsh on the fish and API whitespot/velvet. No improvements.
• increased temps to 86(30c) to speed up the parasitic lifecycle...but this seemed to greatly make things worse and I lost a cory to a secondary bacterial infection. So i brought temps down to 82(28) to try to find a medium to kill whatever this is but not speed up secondary infections.

 

It's probably not parasitic. The vast majority of "parasitic" infections are actually bacterial infections.

 

It's probably not parasitic. The vast majority of "parasitic" infections are actually bacterial infections.

Unfortunately if it is bacterial I will be limited in my treatment, as the EU does not allow antibiotics for fish treatment. I may attempt to find an exotics vet for prescription.

Perhapse a fungus?
You should probably fill out the sick fish form to streamline the information in your post next time.
It seems you have a pretty heavy bioload and might need to up your water changes. Look into a UV filter if you can.
I am a big fan of H2O2 to clean up the water column of single celled organisms and such. It's abundantly available and pretty simple to use. The general method is to remove your filter media, dose up to about 2ppm, let it run for about an hour, then replace your filter media. It will crash a cycle if used improperly, so do additional research before trying.

It does have a fungus like effect, but no fuzz so to speak just a 'silvery/white layer.
As I am in EU medications for both funguses/parasites/bacteria are all quite similar. I've used combos of melachite green/blue, acriflavin, silver proteinate, nitrofurazone, which should have got a fungus.
There are 21 fish in the tank, I thought it would be okay because the fry are around an inch but they are high bioload so will increase waterchanges.
I will look into h202, as I think I plan to tear the tank down and move them into a bare set up.

 

How is your pleco today? Would still like to know what cories you have, if you wouldn't mind.

 

How is your pleco today? Would still like to know what cories you have, if you wouldn't mind.

Sorry was but about to respond to your post.
My pleco is hiding today, behind some wood that I have stuck near the surface on the back wall of the tank. I see some red specks on him so I am concerned he has septacemia but I am holding off on euthanasia as last night he came down from the surface for few hours and was attempting to feed.
My corys are the Black Venezuelans, and they have always been not quite right...very skittish despite lots of hides and I still lost 2 mysteriously at about 2month and 3 months. I ordered another 3 online from a breeder hoping theyd be healthier. One arrived dead and the other two were fairly ill. This was before I had a quarantine tank too.
The usual tank temperature is 25c or 77f. I have read mixed information about whether this is suitable for these types of corys.

 

No sorry for me, and thanks so much for responding.

Wonder if your cories were wild caught? It's not uncommon for them to come in with flukes, and yet you treated for flukes.

Have you referenced SeriouslyFish for temps? I find that site to be extremely helpful at settling unknowns.

 

Thought I'd update in case anyone else was having a problem similar to this.

I realized the Corys/Pleco were most affected by this disease because they spent a large amount of time near or on the substrate. This means the main cause was ich/velvet.

I moved the fish out into two separate tanks, I couldn't get h202(coronavirus issues) but I am running the old tank with lots of salt at 30c/86f for atleast a month.
Infection slowed instantly in the new tanks, but some fish still symptomatic.
I mixed esha 2000 (to treat secondary infections) with waterlife myaxin (ingredients treat ich) with little improvement at first and sadly lost 2 more fish.

So I took a risk and used a low/medium dose of salt with the medications.
Improvements within 3 days, it removed/renewed slime coat which I believe allowed the medicine to reach the scales. White cloudly film on fish reduced very quickly, as did any secondary fungus and white spots, gills are less red.

The pleco which I was going to euthanize has made an unbelievable recovery, all his dark colour back, fungus on fins is gone and has the strength to stick to the glass/ornaments and eat again.
All fish are no longer flashing and breathing returned to normal.
The only fish I still have concerns for are 2 corys, but they are eating and lively still and I'll continue a second treatment for them.