Tetra looking sick, but otherwise active and eating

[nix_nix]

Hi!

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.).

I have a weird looking tetra. One of its front fins (the ones next to the gills) seems to be missing, and it has kind of a bulge on one side at the front.

I shot a video of it. Hopefully it's clear enough to draw a conclusion:

2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Please give exact values.

Temperature: 23°C(73.4°F) (lowered from 25°C(77°F) yesterday).

I'm not sure about the rest because I don't have any equipment with which to measure. If you really need to know, I suppose I can go get some equipment, but my budget is pretty tight right now :/

3~ How large is the tank? How long has the tank been set up?

It's 54 l (14.26 gal) and set up since 2014-09-10.

4~What type of filtration are you using? Please give the name and number (i.e. Fluval 304) and amount of gph if known.

I have a Stingray 15 with zeolite and active carbon cartriges:
Elite Stingray Filter 15: Amazon.co.uk: Pet Supplies

5~How many fish are in the tank? What kinds of fish are they and what are their current sizes?

- 8 tetras about 4 cm (1.6") - two of them (one of which is the one I'm worried about) are bigger by about 0.5 cm (0.2") than the other 6.

- 2 corys about 5 cm(2")

- 1 pleco about 8 cm(3.1")

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?

I changed the water yesterday. I remove approximately 50% every week. I remove the water in such a way that I vacuum the gravel in the process.

7~How long have you had the fish? If the fish is new, how did you acclimate it/them?

It came with the original batch, so beginning of last september, like the tank.

8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.?

Nope :/

9~What kind of food have you been feeding your fish, have you changed their diet recently?

"Natural Color Enhancing .5 mm sinking pellets New Life Spectrum Grow"

I feed my pleco "Tetra Pleco Wafers" every second day, and I put a piece of cucumber in the water to prevent the pleco from eating my plants.

I've started with the wafers and the cucumber about three weeks ago, having made the mistake of assuming the pleco can do OK without extra food. It did a number on my plants. They're recovering now. When I throw in the wafer, all the fish, including the tetras jump on it and inevitably eat some of it, even though it's supposed to be for the pleco.

The other tetras are OK. Only this one. Weird.

 

[Rianyu]

The video is very blurry :T But from your description and the bulge I see in the video it seems to be an injury rather than a disease. I had one of my neons that lost colouring in the middle of its body and it was swollen. Fins looked VERY tattered too but he's healing with clean water and food.

Can you try to get a clearer picture? Until others reply I would just make sure the tank is kept pristine, especially if you can't test the water yourself. You could take a sample to a LFS and see if they can test it for you.

 

[nix_nix]

Here are a few more pictures of the tetra. I see the same stuff on at least two others, but to a lesser extent. They're still apparently all acting normally, eating greedily as ever, schooling, etc.