help! In an established and previously healthy tank, I'm suddenly losing fish right and left. Survivors are lying on bottom, lethargic, not eating, with swollen redness around pectoral fins. Possible introduction of irritants include pine pollen that was finely coated on the python that I used to clean the tank two days ago, or used substrate from a couple of smaller tanks that was added about a month ago. The 5 lbs of used substrate was added from two six gallon eclipse tanks back into the 30 gallon that I had originally borrowed it from for rearing fry. The water in the 30 gallon has had a tendency toward cloudyness ever since I added the substrate back. When I lost a gorgeous snowball pleco and some of the lemon lab fry night before last, I did a 75% water change, added three teaspoons of cichlid salt, raised the temp to 78F. Yesterday I lost two lamp. compressiceps, so did a 10% water change. This morning I had two dead loaches, one clown and one zebra. Noticed a few white spots two other clowns this morning along with a mottled skunk botia and mucous laden striatus so I removed the carbon and put in 13 drops of malochite green into the 30 gallon tank. Feel like I'm grasping at straws here..... the water is still cloudy but fish are beginning to eat and swim around again. Several have the red swollen irritation around pectoral fins. Any suggestions?