Goldfish, Part II
Housing and Maintenance

by Jennifer Wilkinson, CAS
originally published in The Calquarium Volume 41, Number 10, June 1999

This month as promised, I will discuss goldfish housing and maintenance. Should I use a goldfish bowl, aquarium, or pond? What about other containers?

Goldfish get to a very large adult size and need a lot of oxygen. It is recommended that as large a container as possible be used. Its true that a 40-litre aquarium can house two to four small goldfish for a while but they will not reach their full growth potential or be as healthy as they could be.

To properly house goldfish, they (all types) need 75 square centimeters of surface area for every 2 centimeters of goldfish. That means 120 to 200 litres of water for every goldfish. Ponds make the perfect homes for goldfish. Remember fancy goldfish are slower moving than the single tail varieties and should not be housed together. These are also cold water fish, so they should not be housed with tropical fish.

I kept six beautiful bubble-eye goldfish in a 1.2 meter by 2.7-meter indoor pond. This pond was constructed out of wood (2x4s). The inside sides of the pond were lined with good one-sided plywood. The floor inside this frame was lined with Styrofoam. For draining this pond, a two centimeter deep well (about 15 centimeters wide) was left at one end. Then a pond liner was nailed to the top of the wooden frame. The outside and top of the frame was covered in wallboard to match the wall. This is an 800-litre pond. This allowed just over 130 litres of water for each bubble-eye goldfish that I housed in there. A pond pump with a filter box was used. This pump had a bubble fountain attached to it to keep the surface water gently moving. One has to be careful with the fancier goldfish as they can not take a strong water flow into the filter or any strong current caused by the filter.

I also used soft-sided kiddy pools to house some of my goldfish. These pools were larger than the homemade pond. I kept some ryukins, black moors, and orandas in them. On one of the kiddy pools a large inside canister filter was used along with a large outside box filter. The other pools didn’t have any filtration but had fewer fish, and were stocked with water lilies and other pond plants.

Water changes were done about once a month. Because goldfish are cold water fish all we had to do was dump some water (outside) and refill with the hose from the outside tap. Of course, caution must be taken to ensure that the water being put into the pond is approximately the same temperature. With these conditions provided, my goldfish grew, matured, and spawned on a regular basis.

I have housed two orandas in a 270-litre aquarium serviced by an outside canister filter with a sponge on the intake tube so that these clumsy fish didn’t get pulled in. This was a bare aquarium, as goldfish have delicate fins and features that can be damaged by ornaments or plastic plants. Even if these items don’t appear to have rough edges, they can still damage goldfish.

Other smaller containers can be used for quarantine and temporary housing. The idea here is to not leave them in to cramped of quarters for too long a period. Remember that surface area is most important. So a low shallow container with a large surface area is much better than a goldfish bowl with a very small opening in the top. The tall skinny ornamental tanks are simply not suitable for goldfish. Also remember that some of these fancy goldfish are best viewed from the top.

Yes, I have actually used a cat litter pan to quarantine a bubble-eye goldfish for a short while. The litter pan met the requirements of having a large surface area for oxygen exchange, even though it was quite shallow.

I have heard all sorts of people say that they wouldn’t keep goldfish because they are dirty fish. First of all, what does that mean? I take that to mean they put five fancy goldfish in a 40-litre tank, over fed, didn’t do any water changes, and ended up with a dirty tank. I would say that could make these fish dirty fish. In my experience if the above mentioned is avoided there shouldn’t be a problem. My pond, pools, aquaria, and substitute containers were always crystal clear.

Ideal water conditions for goldfish are a pH of 6.8 to 7.6. They can live with a pH as high as 8.0. They prefer moderately hard water but can live in very soft to very hard water. Ammonia poisoning is especially harmful to goldfish, the first signs being blood streaks in their fins. I kept my goldfish in a pH of 7.5 in soft water with no problems.

Goldfish will eat almost any kind of food being fed. If fakes are being fed, they should be soaked in water before feeding to the fish. Feeding dry fakes may cause swim bladder problems and fish swimming upside-down. Pellets are a very common diet for goldfish. Any commercial brand is fine. I fed a variety of small pellets including wheat germ pellets for goldfish. Again I did not feed the larger sites of pellets as they can also cause swim bladder problems. My outdoor fish also got earthworms, assorted bugs, and mosquito larvae. On the very odd occasion they may even have gotten frozen bloodworms.

On one occasion (when I was running the fishroom of a pet store) I had a customer come in and tell me she had a 20-litre aquarium with four fancy goldfish in it. She found another one that she wanted that day. She asked for my opinion, of whether I thought she could fit another one into that tank. I thought that I had convinced her that her aquarium was already overcrowded when she left. A short while later she came back, figuring I wouldn’t be still working in the fish room. So, since she had to deal with me anyway, she told me that she was sure there was enough room to fit just one more. So I bagged the fish she chose, and she went happily on her way. I wondered if that 20-litre aquarium was the one I saw for sale three weeks later? I guess I’ll never know.

On the other hand, when visiting a fellow hobbyist’s house, I was oooing and ahhing over her beautiful koi. Then a very nice red and white fish caught my eye. She began to laugh at me because the approximately 40-centimeter fish was a 10-cent feeder fish that she had bought to seed her pond with. This was a very nice single-tailed goldfish that had brighter coloring than her koi.

Goldfish can be very beautiful if the proper conditions are provided. Lots of room lots of water changes (especially if kept in smaller containers), cooler temperatures (no heater needed as long as temperatures don’t drop below freezing), and lots of oxygen (air exchange). The hobbyist will find that goldfish are not any dirtier than any other fish. These fish are just as challenging, if not more so, than tropical fish. One more thing I have to add here, goldfish are truly not a fish for children. I have been told many times in stores that they don’t need to carry quality goldfish because they are meant for children to keep in goldfish bowls, and it just really didn’t matter. It makes you wonder how one store that specialized in quality goldfish has survived for over 25 years just selling goldfish to the children. I wonder how many four-year-olds buy $300 goldfish?????

Other aquarium clubs and non-profit organizations can use this, or other articles, in their own journals or web sites, provided that credit is given to the author, the Calgary Aquarium Society, and The Calquarium. In the case of a reprint in a hardcopy publication, two copies of the published work are sent to the Calgary Aquarium Society at its mailing address. And in the case of a reprint in an Internet publication, a link back to the original article site must be provided in a prominent location.

Go to Part III, Goldfish Breeding