first of all, tank is too small for so many fishes as said by
many of those who have replied.
secondly, you feel tired changing the water of the tank - your pet
fishes' lives depends on you...if you find changing water a bit
troublesome, i suggest you stop rearing fishes and give it to other
interested parties ( i have tried that, result - my fishes die=it
Suc*s to see your pet fishes die lor) better learn more tips on
rearing fishes or give it away to put it out of misery staying in a
dirty fish tank
thirdly, as said by some, if you are having too many fishes inside
your tank, make sure you jolly well get hold of a super good filter
which cleans the water clearly...there are some filters which
cannot make it, be sure not to buy the wrong ones...
fourthly, your mixing of fishes are wrong...your tiny little fishes
mixing with goldfishes, goldfishes eat a lot, if you don't know
that. so by mixing them together they are very greedy and will eat
all those things that you throw inside...either they eat too much =
bloat to death or your tiny fishes gets nothing to eat during
feeding times...
fifth, tiny fishes need to match with other types of fishes but not
goldfish...it's definately a wrong mix, consult the shop tender for
more questions on mixing of fishes. It's best to keep goldfish
together with goldfish and nothing else..if you can, separate the 2
types of fishes...
six, if you want to rear tiny fishes, i suggest you get some plants
to go with them minus the goldfish....if not your tank will appear
too empty
lastly, i hope you have a wonderful time rearing those fishes to a
healthy growth provided you do some homework and asking around for
help on maintaining your fish tank, if your lazy, then just hire
some experts to help you do the job, they do offer such services.
you can call them if you want. 