i am a little unsure what cycling means? i read an article but i was kind of confusing for me :( If you could pass a good article my way about it id apreciate it :)

I will be getting my water tested today and getting the test kits so ill update on that. And will do the water change aswell.
My ph is 7.5.
I cannot give all the fish back they have nowhere to go or they will die so that is not an option :(

How do i know what my filtration is? I have 2 aquafilters they run constantly.

i will cut down my feedings aswell

i have a temp gage, My temp is allways at 76 everyday.

Here is what my tank looks like today all the fish seem healthy and are active like usual.

@Natalie - It sorta wasnt a mistake, i didnt know what had happened until after. I didnt have a test kit then and couldnt work out what was going on, took a sample into my LFS and the result made more question. Upon getting home and asking some questions of my kids, yeah i got the answer *slapsforehead*

Cycled - The tank builds up beneficial bacteria (BB), these eat the ammonia (which burns fish and makes them unwell or die) produced by the fish/old food/mulm in the tank, the BB turn the ammonia to NitrItes (also not healthy for your fish even at low levels) first, then to NitrAtes (harmful at high levels)
Nitrates are controlled by you when removed with your waterchanges

Prior to moving the tank to your place it would have been cycled, as in tank stats stable to make it a healthy place for fish.

Ammonia 0
NitrIte 0
Nitrate 5-40 (this varies, over 40 you need to waterchange)

You need to know the above stats as they help you know whats going on with your tank :)

When you moved the tank, you kept the filter wet (good thing) and just emptied the water, i assume didnt wash anything in the tank, and just set it back up......this way of doing it means the tank will still be cycled or it may have a minor glitch then will settle again no problems.

Now most of the BB live in the gravel and the filters. 3 weeks after setup you changed ALL the media in the filters. What you essentially did was throw out a good majority of your BB, and the tank has gone back into the cycling process to recover and build back up the BB you removed. The tank is unstable while in the cycling process, ammonia leves rise, then they start to go down and the NitrIte levels rise, then as they drop the NitrAte levels will rise, until the tank is again fully cycled (Ammonia 0, NitrIte 0, NitrAte under 40 (over 40 you need to Water change)

So to stop it happening again, NEVER replace everything in your filters at the same time. Charcoal only lasts a max of 2 weeks anyway, so i would be removing any charcoal and adding in more sponges or some noodles

Now to get you through the re-cycling tank and try to save the fish, you need to do waterchanges. Frequency will be a hit and miss thing because this is where you really need you test kits to know what the levels are.
I would be doing 20% every 2 days for a week, then 10% every 2 days for 2 weeks, then move hem back out to 30% every week

Definately minimise feeding to just what they will eat in a few minutes, excess food will be a big problem otherwise

Hope that explains it for you, if not please ask, we are here to try and help.

thanks that helped alot :) i got ymwater tested (i will be testing it everyweek at the store they do it for free) and all my levels were great it did show a little anomia but he said to just add some real plants and no need to add chemicals because all the levels were good. So i bought some real plants to go in there. And i guess our biggest problem was probally overfeeding them and changing the filters and those 2 things probally led to the fish dying :( so i will be cutting out a feeding aswell.

Also we havent been vacuming the gravel as much as we should so i will be doing that everyweek with a 20% water change and hopefully things work out for me :)

You all have been such a wonderfull help thank you soo much i will keep you updated and i hope everything turn out this was pretty stressfull :(

My tank has been set up for about 4/5 months now, since ive posted this after the fish died, i have been doing lots of research and have been properlly taking care of my fish.

Since this incident i have been doing 20% water changes weekly, checking my levels regularly and everything seems to be doing great.

I found a few reason my fish were dying: bieng overfed, keeping the tank TOO clean, as well as not sifting the gravel as often so ive made some big changes and for the last month or so everything has been doing wonderfull and i even started hand feeding my ghost knife which is very cool. and all the fish seem to be doing great.

Thanks.

yeah i figured that one out!!
lol we now use a 200g resevoir for our tank and have the water sitting for 1 week inbetween water changes. That and simply testing my water has helped trumendusly and since then no fish have died my tank is doing AMAZING :)
It sucked jumping into this i thought it would be so easy!! lol i had alot to learn. Now i think we have it all down and are really looking up information anytime we get a chance to learn new things is just great :)

Check my fish tank out in the member tanks, its surrrrey the one with the ghost knife, i since had added 2 GIANT peruvian snails love them besides the fact that they eat every plant in sight so plants have become a weekly purchase i make but there cheep and look amazing in my tank so i dont mind buying them... just wont be buying anymore 25$ rock plants anymore!!


thanks for the reply :)