Why is my goldfish sitting at the bottom of the tank?

Question

My goldish seems healthy, and is usually VERY active, but lately he's been spending lots of time in one of the bottom corners of the tank (always the same one) just sitting there. If I tap on the glass he'll swim around again, and he does spend a lot of his time swimming like normal. I've never noticed this before. Is he sick? I just changed the water a few days ago and even added the chemical removing stuff to it... The water temp seems cool, maybe 50 something degrees.

He has rocks and plants in his tank, but they are kinda dirty (covered in brown stuff..). If I cleaned it, would that help? The tank is 10 gallons. I'm in a dorm room, and the temperature outside has been around 0 or below the past couple of weeks. My dorm has heat but it gets really hot in here if we turn it on. My goldfish seems very active and likes to scavange for food and swim around across the tank.

Also, he is a small fantail. I've had him for a few months.

I keep forgetting details lol.

I have a filter.

Answer 1

what sized tank is he in? is there a filter? does he have stuff to keep himself busy, like silk plants and such? fancy goldfish or common?
(see here to see what kind he is if you don't know already, this can be important: http://www.kokosgoldfish.com/ftypes.html )

the water temp may also be contributing. if you give a little more info I can help a lot more!

*eidt*
thanks for the additional info. okay, so here are my suggestions:

take the plants out and wash them.
do a 20% water change by siphoning out water from the bottom of the tank.
get a better filter, a thermometer, and a heater.
raise the temp (SLOWLY) to about 70°F
get a mystery snail, sounds like you have an algae problem.
try floating a slice of an orange on the top of the water for the goldfish once every other week. it has vitamins he needs in it.
put a cucumber slice in the bottom of the tank for the snail every other week, removing it after being in the tank for 1 day.
also get liquid calcium for the snail, follow the direction on the bottle. it's usually something like one tsp(5mL) every 3 days for a 10 gallon. I know liquid calcium is made for marine tanks, but most are safe for freshwater, just check the label.

while a 20gallon tank would be a better home, you can get away with a 10gallon, I understand you probably don't have much space if you're dorming.

*edit again*
fantail, good. I was afraid he was common, which would need pond or a very very very large tank.

Answer 2

If it's that cold, he's probably just slowing down in response to the temperature. Goldfish are built to survive very cold water temperatures but their metabolisms slow down in order to do so. It's not unhealthy for him, though you do need to feed him much less while he's sluggish and be sure not to warm the tank up too quickly or you'll shock him to death.

If you want to see him more active, you'll have to slowly raise the temperature with a heater to at least 68 degrees Farenheit or so. Two degrees Farenheit every hour or so is the fastest you should try.

Answer 3

Gold fish love warm water, make sure you have a good filter, It pays to have a few snails to clean the tank, but make sure you feed goldfish so he (or she) isn't hungry otherwise they will then eat the snail, I find it is good to have plants to keep the oxygen level high but if they start looking gross either clean them or get new ones (which i do to keep the tank looking healthy and is healthy for my fantail). What do you feed your fantail, i feed mine pelets and special goldfish flakes for healthy goldfish, so a good food is a advantage

Answer 4

The tank is way too cold. His body will be shutting down for the winter. Don't feed him at this temperature at all. Make sure you test the water and keep ammonia at zero.

Answer 5

he's either depressed, or is dying. you shold make the water temp. higher, or go to the vet

Answer 6

You don't have a thermometer?

Answer 7

it is probably dead. i had a fish that did that and it was dead.