blister like growth on tail fin of my Black Moor (Scuba)

Question
QUESTION: I have just noticed a blister like growth on the tail fin of Scuba, my black moor. What could this be.
ANSWER: Hi Karen
Few questions for you first.
What color is the growth?
Does it look cottony, smooth, open sore like an ulcer?
Any other symptoms, like, lethargy, darting around the tank, rubbing on objects in the tank, not eating, hanging at the top a lot, gasping for air at the top?  Anything unusual?
How many fish and what kind are in the tank?
What size is the tank?
How long's the tank been set up?
Do you have a test kit, and know what the ammonia, nitrites, and nitrates are reading?
And, finally, how often do you do water changes?

Let me know so we can try to figure it out!

Christy

---------- FOLLOW-UP ----------

QUESTION: Hi Christy, It is not an open sore but rather smooth and the same color as the black fin, almost looks transparant like a water blister.  It is a 40 gallan tank and has been established for over 2 years.  It is a hexagon tank and has 1 lionhead goldfish, 1 oranda, 1 orange/black ryunkin, 1 calico fantail and of course the black moor"Scuba".The tank has a water change once a month or biweekly if needed.  The tank is in my sunroom so does get a lot of light and at times, algae can be a problem.  The tank is areated.  Thanks for your help

Answer
FOLLOW UP:  Hey Karen
Thanks for the great ratings!!  Every one has their opinions on how much water to change and how often.  Doing them more frequently is better(my opinion), because it helps dilute or remove the toxins that build up-ammonia, nitrite, and even nitrate at higher levels is bad.  I just read an article that was talking about that, and how if you let it go too long, the ph can drop suddenly, then you do a change and it alters it again, which is stressful for the fish. I think it's actually less "shocking" for the fish doing it weekly.  
I've even had tanks before where I changed out 50% of the water once a week, had an oscar(messy fish as well), and he did fine with that.  I've read where people do that large of a change even without messy fish.  It's a personal preference I think, but I do believe it should be done on a weekly basis to keep everything in order.  

Best regards,
Christy


Hi Karen
I'm afraid I don't know what that could be.  I have 2 possibilities, but I still suggest checking with an expert that's more familiar with goldfish.

The first, goldfish especially black moors are known to change color.  But you're saying it's the same color as the fin, so don't think this is it.

The second, a fish can get ammonia burns, and usually we see them when they're healing, the spot will turn black.  Now being a black fish already, it may not show up, but I don't know if the burns actually cause a blister.  So not sure on this thought.

One thing though, your tank is a tad overstocked, usually with goldies they recommend 15 gallons per goldie, some say 10 is sufficient.  You should up your water changes to once a week.  I usually recommend once a week, vacuuming the gravel and changing abou 25% of the water.  With your tank, I'd do 25-30% of a water change once a week.  That may help as well with the algae, or help control it a bit anyway by reducing the nitrates it loves to feed on(in addition to the extra light :).  Not sure what the blister thing is, but the extra water changes may help that as well, especially if it's something related to water quality.  You could also add some PimaFix to the water.  It's a natural remedy that won't hurt the fish, or the water quality.  It's good for fungal and gram negative bacterial infections.  Especially if the spot breaks open, that'll leave the fish open to infections.

Sorry I couldn't help any more then that, like I said, try someone more familiar with goldies.

Christy