My goldfish's tail has suddenly developed a black edge -- the end of his tail is dark for maybe half a millimeter. I think the very tips of his pectoral fins are dark too. What could this be? The other fish is fine.
Tank parameters (ppm
water hardness: 25
alkalinity: 40-80 (hard to tell the difference on the test strips)
These parameters have been stable since just after starting the cycling.
Also I checked the ammonia today, and it was 0-0.25 ppm
(again, test is hard to read).
Temperature varies a bit over the course of the day, from 75 F to 78 F or so.
Tank is 12 gallons. Cycled for about a week, has had the two goldfish for about a week. They're little goldfish -- I know when they get bigger they'll need a larger space. Right now they're about 6 cm long each.
Filtration: Bio Wheel - comes with Eclipse System 12 tank. Box claims 150gph.
5~How many fish are in the tank? What kinds of fish are they and what are their current sizes?
2 goldfish, 6cm 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?
Haven't done this since setting up the tank almost a week ago.
7~How long have you had the fish? If the fish is new, how did you acclimate it/them?
I've had the fish for about three weeks now I think.
8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.?
No, just the stuff that was in there while the tank cycled.
9A~What kind of food have you been feeding your fish, have you changed their diet recently?
Feeding them goldfish flakes (Top Fin brand) and occasionally sinking granules (Tetra brand). Gave them some freeze-dried bloodworms yesterday.