Killer Goldfish

Question
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Followup To
Question -
Hi,
We have one goldfish (fresh water tank, no filter). My question is - Our fish is about a year old now. Over that year we've introduced several 'friends' to it, but within a couple of days they're floating on the top! is it possible that our goldfish is killing them, or could it be passing on some disease to them (but it's fine itself)? Also, do goldfish get lonely? We keep thinking it can't be much of a lifr to it, in there by itself, but I don't want to keep bringing it friends if they're all going to die!
Thanks



Answer -
Hi Kate;

Without a filter, your tank probably can't support more than one fish at a time. The new fish will be stressed from getting a new home and sucumb to lower oxygen levels easier than your current fish, which is accustomed to it.

How big is the tank?
How often do you clean it?

Followups welcome

At Your Service;
Chris Robbins

Thanks for answering! The tank is actually pretty big for just one goldfish (about a foot and a half long, a foot high?), we don't clean out that often as we were told in the pet shop that could distress the fish. We change half the water once a week(ish) and do the whole lot every month or so. We always leave the new water in a bucket overnight before we put it in the tank. Do you think we need a filter?
Thanks.
Kate

Answer
Hi Kate;

Changing water once a week is great. Cleaning the whole tank out is very stressful for the fish, and should be done very seldom. Partial water changes are best. I think the size tank you have is fine for one goldfish until he gets about 3 inches or so. Then he needs a bigger tank. They get too big to have more than one in a tank that size.

Goldfish get to be 8 inches long, sometimes more. They are deep-bodied, messy fish and require plenty of space. If you want to keep more than one goldfish, get a 55 gallon (or bigger)with a power filter and extra air bubbles from an airstone hooked to an air pump. I have kept up to 6 in a 55 that way as long as I don't overfeed and change at least 25% of the water at least once a week.

In my opinion, unless you have massive amounts of live plants that provide oxygen, goldfish need a filter. A power filter that hangs on the back is a good choice. If you ever notice him up at the top of the tank as if he is eating and there is no food, this means he lacks oxygen and is trying to get some. The filter will provide that for him by agitating the water.

Followups welcome

At Your Service;
Chris Robbins