Help: Internal bacterial or parasitic infection?

[noncentric]

1~What type of fish is afflicted? In addition, please describe what is wrong with the fish to the best of your ability (i.e. cotton like growth, bloated, etc.).

So, I think some of my zebra danios have an internal infection.

I had 6, then one got really listless and skinny and I moved it to my 6-gal (which had 2 ghost shrimp at the time, no minnows) - the other 5 danios seemed fine. That fish disappeared overnight a few days after being moved. I figured that the ghost shrimp must've eaten him, since there was no sign of his body anywhere inside or outside the tank.

I got the minnows, and moved the 2 ghost shrimp to the 25-gal so the minnows would have the 6-gal to themselves. One ghost shrimp got lethargic and died, while the other seemed fine. A few days later (yesterday), that second ghost shrimp also got lethargic and died and I noticed that 1 of my 5 zebra danios was behaving/appearing like the 1 that had died a while back. And today a 2nd zebra danio looks in poor condition too.

I suspect there is some internal bacteria or parasite in the 25-gal - probably originating from the ghost shrimp. The 2nd (and final) ghost shrimp that died yesterday had something protruding from it's anterior underside (near its mouth). Looked like it might be a worm of some kind, but I'm not sure.
EDIT: found a picture that looks like what was protruding from my shrimp
http://www.fishpalace.org/bacterial_laura.jpg

The 2 sick zebra danios don't have any external signs, just skinny, lethargic (they hang out by themselves), inappetant (they swim around the food, but don't eat), and one's dorsal fin is always upright. No redness, no external growths, no white spots, and no abnormal breathing.

I'm trying to decide what to treat with - I want to treat the entire tank, so something safe for live plants and otos:
Is Maracyn-II a good choice? Looks like it's a 5-day treatment (with a double-dose the first day).
Is there something else I should use instead of, or in conjunction with Maracyn-II?

Thanks! (Additional info below)

2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)?
(AP FW Master test kit): ammonia=0, nitrite=0, nitrates=5-10
pH=7.0, temp 79 F, live plants, no CO2

3~ How large is the tank? How long has the tank been set up?
25-gallons, set-up 3 months ago

4~What type of filtration are you using?
It's an Eclipse-2 hood, 200 GPH. No carbon, just mechanical (filter pads) and biological (bio-wheel).

5~How many fish are in the tank? What kinds of fish are they and what are their current sizes?
5 zebra danios and 2 otos (1.5" each)

6~When is the last time you did a water change and vacuum the gravel? How often do you do this? How much water do you remove at a time?
Major vacuuming and plant trimming yesterday (Monday), along with 30% PWC. I do 30% PWC every 8-10 days.

7~How long have you had the fish? If the fish is new, how did you acclimate it/them?
Had the zebra danios 3 months, otos for 2 months.

8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.?
Moved the ghost shrimp from 6-gal to 25-gal. Newest plants are 6 weeks old. Addition to food menu (Omega One Veggie flakes) 1 month ago.

9~What kind of food have you been feeding your fish, have you changed their diet recently?
Tropical Flake food since origination of tank. Omega One Veggie flakes since last month month ago. Occasional (1/week) blanched zucchini and de-shelled peas.

 

[Zagz]

If the pic resembles your fish then Maracyn II would be a good choice in meds IMO. Remove any active carbon from your filter and I usually do a water change before I begin treatment.

 

[Devilishturtles]

Hard to tell. Could be either. From the sounds of it, it sounds more bacterial than anything. Maracyn-Two is a good choice and your plants should be fine. Just keep an eye out for your water parameters, namely ammonia, spiking. Antibiotics like to fool with your water sometimes.

I know other people have done this also, which is to feed an anti-parasitic food as soon as the fish start eating. That way you can get both meds in the fish. I would not, however, treat your water with both meds at the same time.

Just my opinion, HTH

 

[noncentric]

Thanks Zagz, the pic is similar to what was on the last ghost shrimp that died (no more shrimp now) - so far (knock-on-wood) none of the fish are showing any external signs, except for being thinner and listless.

Thanks Devilishturtles, I'll definitely keep checking the water params. I'll also look into getting the anti-parasite stuff.

I'm mainly hoping to hit the tank with something that will attack the most likely problem, and then use a secondary treatment if that first attack doesn't work...so an anti-bacterial followed by an anti-parasitic sounds like a good plan.