you guys should check out fnzas site if you are interested in fish keeping
to anyone new to fish keeping or has had many fish die there are 2 major rules you need to follow
1, cycling a fish tank (google it, the process of establishing good bacteria in a filter to remove harmful ammonia from fish waste an over feeding) if your filter is dirty THATS GOOD, its fine to "unclog" any fish tank filter every clean but under no circumstances should you rinse it completely clean EVER, this is a really important thing to avoid!
2. chlorine , alot of towns use chlorine in the water, its fine for the fish but its not fine for the good bacteria that builds up in a tank, it kills it off an them flushes dead bacteria around the tank - THIS reason alone is why most people have losses when cleaning a tank or putting new water in a tank
I have kept/keep lots of fish, my current tank is about 280L an houses cichlids, sunshine peacocks an moliwe kribensis (not the common ones sold in shops)
was gona put some pics up but they are pretty terrible quality haha