Starting up a freshwater aquarium? My son is an absolute addict when it comes to his aquarium. However despite doing everything "right" (or so I thought) His gold fish died to day. We have had him for 5 months and everything was fine even last night at bed time he was fine but today at about 11 am he was dead. Connor is ditsraught and I have assured him we will replace nemo but not for a week cause I want research time and I want to do EVERYTHING PERFECTLY this time. I can't go thru this again. So PLEASE I NEED instructions and advice on startng up a 15 gallon fresh water aquarium and I really would like to hear from some people with SERIOUS FRESH WATER AQUARIUM EXPERIENCE!!! Thanks so much I have a truly broken hearted 5 year old who took AWESOME care of his tank and can't understand what went wrong. I don't want this to happen again.

< class="additional-details">Additional Details 1 day ago Here are some details. We have 15 gallon that contained 1 golden fantail. Everything was fine til christmas when we went a way for a couple weeks and we had algae growth when we came back (see a previous question I posted on here) and I scraped it clean due to advice I got on here. I changed my filters frequently like I was told cause goldfish are "very dirty" fish and day before yesterday I changed filter and did 25% water change (could this have killed him ?) . Any help with why he died would be appreciated also. 1 day ago Hi thanks for all the good advice from what everyone has said I did everything right so I guess we just had defective fish. And to poxxyfoxxy listen idiot... I AM INVOLVED !!! I over see everything he does with his fish. He wants to do it "on his own" but I know better than to just leave him to it. I AM INVOLVED and you don't have to tell me about "quality time with my youngster" I am a stay at home mom who is considering homeschooling since I used to teach. As for him being at a responsible age my son is more responsible than most kids twice his age and supports his tank with his allownace at 5 bucks a week that leaves him with nothing to spend on toys and he's OK with that. He is heartsick because he can't figure out why he did everything right and his fish still died. From everything I've read on here (including from YOU) Connor and I did everything right so you can give your opinions and advice alike to someone else I don't need or want them!! OK.. if the tank is 5 months old, then the initial cycling isn't the problem.

Possible causes.

Water changes - do you use a water treatment like Prime? If your tap water contains Chloramine it can kill fish and is very difficult to remove remove without chemicals. That could account for the fish going from healthy to dead overnight.

Filter changes. It's important to leave the bio-media in the filter as undisturbed as possible. If you change all the media at once you remove most of the bacteria that provide the bio-filtration. I don't think that's the case here though as it would have taken a while for the ammonia to build up and kill your fish, and it would have looked sick for a while before it died.

Cause 3 - just plain bad luck. Sometimes fish just suddenly die for no obvious reason in spite of us doing everything right.

Your tank isn't ridiculously small for a fancy goldfish, and you do have a power filter. It may outgrow it eventually, but it's going to take a while.

What I suggest you do is get a sample of the water tested at the shop. If it shows no problems get another fish and add it to the tank after a partial water change. It is probably better to restock the tank as it is rather than stripping the tank and having to re-cycle the water.

I dont think you are doing anything seriously wrong and the sudden mysterious death may have been just that.

Good Luck

Ian