Started new tank, concerns about fish dying

Question
Hi, I have gotten a used 37 gallon fish tank (eclipse) and I've got it all setup and added some starter fish about a week ago. Problem is, we started out with a mix of 8 tropical fish, a couple of swordtails, black tetra's, mollies, zebra danios. Over the weekend, one day after I added the fish, one molly died. We replaced it and added also two harlequin tetras. Ever since, almost daily now, fish have been dying. I don't understand, I had my water tested and they said it was perfect. I am noticing that my water (after the tank has been running 1.5 weeks now) is starting to get very dirty looking, with tiny white particles floating in it. I have been feeding the fish a pinch of flake food in the morning, making sure they eat all or at least the biggest portion of it. They also get a pinch at night when I come in from work. Also, I have been feeding them some bloodworms, two times so far. The way the water looks worries me though, I have one harlequin tetra that is just floating around with it's mouth wide open. Others that have died have been twirling around, bumping against the aquarium glass, sinking down to the gravel and swimming up again until they sink again. It is heart breaking to watch and I don't know what to do about it. Can you help break the cycle? I really need some guidance. I appreciate it very much!!

Answer
Hi Rudy,
Sorry to hear about your fish. Although the water is said to be perfect, I wouldn't think it would be. Your fish are dying too fast and their symptoms match up with water quality problems more than anything. The white particles are likely a bacterial bloom starting to develop.

The best thing you can do is to get your own test kit and test the water everyday and take notes of the readings. Do a 30-50% water change for now daily and with the help of the test kit--whenever the ammonia gets into the caution zone. Make sure the replacement water is always dechlorinated and equal in temp to your tank.

If you need more help on cycling read here-
http://www.firsttankguide.net/cycle.php

With the tank being new and all, it has to be going through its cycling phase, which always results in ammonia spiking. And especially so since you stocked the aquarium really too soon with too many fish at a time.

But keep up hope. Best wishes!
Karen~