goldfish always die

[Rose]

I'm wondering about goldfish. I have 2 aquariums. 1 is a 10 gallon glass and the other is a 5 gallon acrylic. Both have the same water, gravel, filter etc but, while the 3 fishies in the small tank are thriving...each and every goldfish I put into the larger tank live for about 3 weeks and then die. I have cleaned the tank...no soap whatsoever, filled it, put drops of aquasafe in and used some of the water from the healthy aquarium and let it run for 24 hours before introducing new fish. They die. I've treated it with fungus med...they die. I have changed the water 1/3 at a time and ..they die. The other little tank is fine. There are 3 fish in the larger tank but I expect they'll be gone soon. Both tanks are in the same location and the fish eat the same food. Very odd. Anyway, could the large tank be toxic? Maybe the sealant (which is all over the bottom seams) be what's killing them? I find this very odd. It was a brand new still in the box tank when I bought it and I always buy goldfish which are supposed to be a heartier fish but I'm stumped.
Thanks for any input..
R

[fernival brainard]

Hi there, good to meet ya!!! Have you tested the water in the tank that everything dies in?

What are the parameters?? temp. ph. ammonia, nitrIte\trAte????

Something "fishy" is definetly going on in there....and I can almost guarentee that somebody here will be able to help you figure it out!

fern

[Sniperelite8243]

when you say you cleaned the tank did you clean the gravel. do you have a powerfull filter that can handel that size tank.if they have the same filter is the one on the 10 ment for the five? goldfish are actually a pretty hard fish to keep since they are prone to s die swim bladder disease. do they stop swimming before they die, float or sink, have you noticed if they are pooing. this question could be important actually. does it look like they have salt on it before they died. also could you give aus a list of all chemicals ever used in the tank. but im pretty sure you could find somebody here that knows a thing or two about fish

welcome to the forum

[BMueller777]

Is the tank cycled?