How to keep water cold for goldfish?

Goldfish will tolerate a fairly wide range of temperature. Anything between 16C - 23C (~60F - 72F) is fine. They will tolerate water that is a bit warmer, but in warmer temperatures, oxygen levels decrease and goldfish need a LOT of oxygen.

The biggest problem you have is the size of your tank. Common goldfish and other single tailed goldfish need a bare minimum 55 gallon tank and an additional 50 gallons of water for each additional single tail goldfish. Commons, Comets and Shubunkins are actually intended for ponds as they get quite large and are very strong swimmers needing a LOT of space. Fancy goldfish such as fantails, orandas, moors and ryunkins need a 20 gallon tank for the first goldfish and an additional 10 gallons of water for each additional fish - minimum. Very strong filtration is also necessary.

Your tank is far too small for even a single fancy goldfish! Also, the small size is what is causing your water temperature to become too warm. NEVER add ice or frozen bottles of water into a goldfish tank.... EVER as the abrupt change in temperature will kill your fish! Your tiny tank is really only suitable for a couple of plants and an apple or mystery snail. It is not large enough to provide a healthy environment for any fish.

Goldfish are notorious for being unkind to live plants. They will eat most live plants, so silk plants are recommended unless you have a large tank in which you can provide live plants intended for food and others for ornamental purposes.

To fix your problem, you need to return the comet or find someone with a pond to take it or you need to get a 55 gallon tank with a very good filter. If your other goldfish is a single tail as well, you need a 125 gallon tank. If your other goldfish is a fancy you will need two separate tanks as single tails and fancy goldfish should not be kept together. The fancy goldfish do not swim well enough to compete for food.

http://goldfishinfo.com/

NOTE 1: There is a lot of misinformation circulating regarding the potential size of adult goldfish! Single tailed goldfish reach longer lengths than fancy goldfish, but they do not reach lengths "way longer than a foot". Here is the truth:

Single tail goldfish:

Commons (often sold as feeders): 11 - 15 inches including the tail. Most are in the range of 10 - 13 inches

Comets & Shubunkin - 8 - 10 inches NOT including the tail

Fancy Goldfish:

6 - 9 inches not including the ornamental tail. There are over 280 varieties of fancy goldfish and how long each will get depends upon the variety.

HI Emi, I now it comes as a shock that Goldfish need vast tanks, huge filtration, a degree of skill & are a constant money pit but it's true! The links below should provide all the evidence you need, by the way-I was just as sceptical when I first got into fishkeeping!

the only stable way to keep a tank chilled for goldfish is a chiller, which usually cost four times as much as the fish, tank, and filter put together!

the only way in indoor tanks without a chiller is to make sure theres plenty of surface movement, and in the summer you can have a fan a foot or so away from the tank also blowing over the surface of the water, but you're still going to find the temperature fluctuating.

your tank is too small for your goldfish, check the link below for goldfish care. common goldfish do best in large pond environments really. commons and fancies shouldn't be mixed, a common can bully a fancy and out compete it to food, if the fancies are bullied their very delicate swimbladders can be irreparably damaged.

I recommend you take your fish back for several reasons:

#1 your tank is too small entirely. Fancy goldfish need at least 30 gallons for 1 fish, and 10 gallons for each additional one. Comets need MUCH more. Comets get to way over a foot long, did you know? It's not true that they grow to the size of their tank - they get stunted leading to ill health, many problems, and eventually very early death. You need probably about an 80 gallon to keep those two fish.

#2 it will become very hot for the fish in summer. You can help by freezing bottles of water and putting them in the tank - they will cool the tank down slowly - but this is a lot of hassle.

If you are determined to keep these, you need at least 80 gallons, and you need to have room to be able to keep at last 2/3 bottles of frozen water in the freezer at a time - maybe more.

EDIT:

''Commons (often sold as feeders): 11 - 15 inches including the tail. Most are in the range of 10 - 13 inches

Comets & Shubunkin - 8 - 10 inches NOT including the tail''

12 inches = 1 foot.

Sorry, shall I remove the 'way'? They still have the capacity to grow to over a foot. Every other bit of my post is the truth, sorry if I haven't kept comets before and added a couple of inches but the rest of my post holds up.

u dont have tokeep it cold but your tank is to small for the two goldfish as they will out grow the tank fast.

i dont think your suppose to have cold water. you will give it a shock and die!

sorry my website is in the living room with fish swimming in it. the water doesnt have to stay cold. just dont put a heater in your tank. the water will stay room temp..& its ok.

Temp is fine I have a heater on my goldfish.

Tank is small for two goldfish.

i dont no why u want to make the water colder my gold fish die when there water gets to cold i have 4 gold fish in a round bowl in my lounge room that just stays at room temp n there fine but i have 3 in my room that have to have a heater cos they hate cold water

You can keep it cold by using ice cubes, just make sure you mix it up real well.