comets have stumps for fins

Question
Hi Chris--

Thanks for the tank advice--I can see that it is getting cramped in there...  So to clarify, are you saying the healthy looking, yet oddly stumpy fins are a result of a tank that is too small? Is it because the others bite them off from the stress of being crowded? Or do the fins fall off or shrink on their own? They get along fine and do not have any missing scales that would indicate being picked on.  And am I to expect eventually all the fins on every fish will go the same way?  Wow--I've never seen this happen!
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Followup To

Question -
My kids have a small tank, approx 2.5 gallons, which held 5 tiny comets they won at a festival.  The fish have thrived and grown so that they are now about 1.5"-2.5" long, but recently, I've noticed that two of them have only stumps for pectoral fins and the dorsal fins are practically nonexistent.  There is no evidence of fungus or raggedness to the tail and the stumps have no bumps, spots or bleeding.  A third fish has a complete dorsal fin but its pectoral fins are stumps too.  I can't say for sure how they looked like when we got them, but they look strange and yet swim fine.  The remaining fish look completely normal.  I don't know the PH, ammonia or nitrite levels of the water.  Any idea what this could be if not a birth defect?  Thanks

Answer -
Hi Ann;

Wow! You've been very lucky and must be dilligent about making water changes and keeping the tank clean. The tank is just far too small for goldfish though, even just one can't make it in there long term. They will soon lose more than their fins I'm afraid and they will slowly die off one by one in spite of receiving excellent care. Goldfish get to be about 8 inches long and are deep-bodied very messy guys, so they create a tremendous amount of waste. They actually need at least 10 gallons of water per fish in anticipation of that adult size, with good filtration. Here is a good web page about goldfish and their needs;

http://www.goldfishinfo.com/setup1.htm

You've done an excellent job caring for them so far. You will definately have to upgrade to a 50 gallon or so though. Even a 30 gallon would be a good change for now. I hope all goes well. Keep up the good work.....

At Your Service;
Chris Robbins

Answer
Hi Ann;

Goldfish tend to just nibble at everything all the time. They may be doing it even at night when you can't see them. It could also be that being so crowded just rubs their fins down. They will probably grow nice beautiful long fins once they are in a bigger tank. As long as the fins aren't damaged at the base where the fleshier joint area is, they will grow back.

Followups welcome....

At Your Service;
Chris Robbins