Why do my goldfish keep dying?

[MrYossu]

Hello,

I have a 24" cube tank, which has a substrate of crushed coral (it used to house cichlids), a large piece of mopani wood and a couple of plastic plants. Filtration is via a Hydor Prime canister filter. I do 20%-30% water changes every week or two.

I put in four goldfish some months ago, which seemed to be doing OK at first. However, after a few weeks, one of them started sitting on the gravel and not moving much. After a day or so, it was dead. One by one, the others did the same. I bought some more, but the same thing happened. I'm down to one goldfish, which seems healthy enough.

I realise that it's a bit of a vague question, but can anyone advise as to why I can't seem to keep the goldfish alive? I would really like to buy more, but don't want to if they are going to die after a few weeks.

Thanks for any help

[imma24]

You are right in not buying anymore -

That size tank is waaaay too small for 1 goldfish let alone 4

My guess is that the ammonia level in your tank is really high. I am assuming you are not familiar with the concept of cycling a tank before adding fish or with knowing your water parameters via testing the water - you should also know that goldfish grow quite large and produce lots of waste so they need more space - like at least 45 gallons for 1 or a pond.

I would try and rehome whatever goldfish you have left in the tank, read up on cycling and get fish that are better suited for that size tank.

Edit: am I incorrect in assuming this tank is too small? Is a 24" cube that large?

[Trillianne]

Firstly... how many gallons is your tank? (I"m guessing 60 based on the dimensions you did give)

What are your water readings for Ammonia/Nitrite and Nitrate? - I strongly suspect this issue is cycling related.

What kind of goldfish are you attempting? (Fancy or feeders/comets)

[MrYossu]

Hello,

Thanks to both of you for the replies. As it happens, I know about cycling very well, having kept tropical fish and cichlids for many years. I don't think that's the problem here, as I seeded the filter with sponges from a very mature tank, so the bacteria should have been there from the start. Also, the tank was prepared for the goldfish right after removing the cichlids, so the gravel and rocks would still have held plenty of bacteria.

Furthermore, the goldfish I put in were pretty small, so even with the fact that they are more messy than cichlids, I would be surprised if cycling or contamination were issues. I had 20-24 cichlids in the tank at any one time, most of them bigger than the goldfish, so I would have thought that the amount of waste from that many fish was more than four small goldfish would produce. Maybe I'm wrong, but I would be surprised if this was the issue. Feel free to correct me if I'm wrong, I'm no expert on goldfish, but I know a fair bit about keeping tropicals and cichlids.

24" cube works out at around 220 litres, and these were plain ordinary goldfish, not fancy ones.

Thanks again

[Honey Badger 1]

It still might be a parameter issue. 20 - 30 % every week to every other week really isn't much of a water change, especially when the tank was so heavily stocked prior to the goldfish.
We really need to know the ammonia, nitrite, and nitrate levels. I suspect that because you did such small water changes the nitrates might be at toxic levels to the new fish.

[Cliff]

+1 to Mommy1's post

and these were plain ordinary goldfish, not fancy ones.

Plain ordinary gold fish are typically common gold fish and will get to be over a foot in size (link below). At some point you will need to rehome them

http://www.aquaticcommunity.com/aqua...ad.php?t=47133

[Tiari]

I have to agree that the tank is too small for common goldfish.

That said, I think the initial issue may be the crushed coral substrate. Crushed coral will make for a pretty high PH, too high for keeping Goldfish.