Harlequin Rasboras Dying One At A Time

[Ceramicbull]

Tank size: 29 USG
pH: 7.8
ammonia: 0
nitrite: 0
nitrate: out of fluid
kH: unknown, but fairly high
gH: unknown, but fairly high
tank temp: 80 F
(yes, it has been cycled)

Fish Symptoms (include full description including lesion, color, location, fish behavior):
One by one, my Harlequins seem to leave the shoal, and twitch until they pass away. They will still respond to stimuli, such as another fish swimming by, and I have seen them feed in this condition. Toward the end, they seem to get a bit of a white coating along the top of their body, and I noticed the tail fin was degraded on one of the unfortunate victims. It was more of a coating than spots or growths. It didn't look cottony. Dead Skin possibly? Fungus? Bacteria? Columnaris? Neon Tetra Disease? The fish seem to last about a week between when the twitching starts and when they pass on.

Volume and Frequency of water changes: At least 5 gal once a week. Sometimes more. API's Stress Coat for conditioner.

Chemical Additives or Media in your tank:
Marineland Penguin 200 filter packs do include carbon. It has a biowheel for the bio filtration. I know I should remove carbon with most medicines, but I suspect that a significant amount of my good bacteria are on my filter pack. Should I gut the carbon out of it and leave the rest of it intact?

Tank inhabitants:
8x Pacific Blue Eye (Pseudomugil signifer)
6x Harlequin Rasbora, down from 8x
5x Emerald Green Cory (Brochis Splendens)
1x Pearl Gourami (Trichogaster leerii)
1x Clown Pleco (Panaque maccus)

Recent additions to your tank (living or decoration):
The Harlequins were added with a sword plant of some type and a bamboo. The first harlequin started twitching about a week ago, when and because of the degraded fin, I suspected fungus and added the fungus treatment. The first fish passed, then a second one got sick and then I added the treatment again. The second fish passed, and then after waiting a while added the gourami and pleco. Now the 3rd fish has gotten sick. None of the other fish in the tank have shown any signs of illness.

Exposure to chemicals:
Tried using Jungle's "Fungus Clear Tank Buddies" (active ingredients: Nitrofurazone, Furazolidone, Potassium Dichromate)
I bought some Maracyn plus antibiotics, but haven't added it, waiting to make sure it won't damage my Filter Bacteria.


Digital photo (include if possible): current fish has no external symptoms, other than twitching, yet.

 

[WILDER]

Do the fish show any of these symtoms.

Flicking and rubbing.
Excess mucas.
Darting, erratic swimming.
Gasping, or laboured breathing.
Red sores or red pin prick marks.
Any redness to the white patches.
Any strands coming out of the white patch.
Any lumps beneath the skin in the white patch area.
What does it look like when your fish go to the toilet.
Do any fish look skinny or bloated.
Check the anus is not enlarged or red and inflamed.
Do any fish have sunken in bellys.
Do any fish have bent spines.
Do any of the fish barrel roll.

Has your ph changed.
Does the white coating look like milk on the fish.
Does the white film look like talc.
Does the white film go down the sides of the fish to form a saddle shape.

 

[Ceramicbull]

Flicking and rubbing. no rubbing against objects. I'm not sure what flicking refers to.
Excess mucas. Certainly could be what the film was, it was not visible on any of the dead fish, but by then the Brochis, if not the pleco, had been nibbling at the corpse.
Darting, erratic swimming. Very much so, they just swim forward about an inch, and then kind of hover back to where they were.
Gasping, or laboured breathing. nope.
Red sores or red pin prick marks. I don't think so, hard to tell since the fish are so orange.
Any redness to the white patches. I can't say at this point, the currently affected fish hasn't developed the white patches yet.
Any strands coming out of the white patch. No
Any lumps beneath the skin in the white patch area. Nope
What does it look like when your fish go to the toilet. I will make an effort to watch the fish poop, so far, no luck. It did just eat so it is bound to happen sometime.
Do any fish look skinny or bloated. Nope
Check the anus is not enlarged or red and inflamed. nope
Do any fish have sunken in bellys. nope
Do any fish have bent spines. nope
Do any of the fish barrel roll. Nope, the fish seems largely in control of its actions, except the twitching motion. Right now it seems to be doing fairly well and is staying with the shoal, actually.
Has your ph changed. huh, it is a bit lower than 7.8. somewhere between 7.4 and 7.8.
Does the white coating look like milk on the fish. as I remember it was whitish-grey, and generally smooth.
Does the white film look like talc. Not really
Does the white film go down the sides of the fish to form a saddle shape. Not as far as I've noticed

 

[WILDER]

Does it look like something irritating the fish.


The symtoms are pointing towards columnaris, parasites.

 

[Ceramicbull]

Irritating the fish? I would guess so. However, thankfully, the fish seems to have beaten it on its own?! It has returned to the shoal and is swimming normally with the others. I imagine it would still be good to treat the tank, though. Any good medicines for Columnaris/parasites I could use as a preventative measure?

 

[WILDER]

I would hold off medicating if the fish hasn't the greyish white film anymore.
Is he still rubbing himself like he has an itch.