ok.. apparently, i don't know what i'm doing. so i will explain myself so all the people that are old enough to be my grand children will be satisfied that i know what i'm doing.
i have (it is sitting empty now) a 150 gallon tank. it had 6 medium sized cichla in it. my son was arrested out of frustration and worry i sat up all night doing tank maintenance on the 150 while going nuts. at about 5 am they called and said i could pick up my son at the jail, so i went and got him. when i came home ALL of my cichla in the 150 were dead. i tested the water, it was all good. ammonia 0, nitrites 0, nitrates less than 20ppm (i had just done a huge water change with ro/di water, not tap water). but i found out that i had been careless and ruined my air pump which in turn took out 2 foam filters and left the fluval 405 as the only filtration on the tank with no extra aeration. it's the ONLY cause i could find.
my son and i did a flush and clean.. we flushed all the stuff out of the gravel till it was only clear water. we pulled the filter and washed it thoroughly, put the bio-media in the dishwasher (with no soap, just on the sani-rinse), along with all of the filter parts. i reassembled the filter, took the seeded filter off of the other tank, put 2 of the filter pads from that tank into this filter, filled the tank, turned on the filters and the heaters. i also took 2 seeded foam filters from the other tank and squeezed them out in the tank and then put them back where they came from. and i replaced the foam filters that were in the tank with the fish died, and bought a new air pump.
i then cycled my tank, being VERY careful to add more bio material every day until it was fully cycled. and then i moved 2 of the larger cichla from the other tank into the 150.
THEN.. a few weeks later the 5 cichla that i spoke of previously became available, so i got them. moved the 2 big guys back to the other tank, and put these guys in (they were all in the 6 - 10" range). i got the bag of massivore with the fish, but i didn't try to give it to them right away. i typically don't feed fish the same day i put them in a tank because they don't usually eat. 2 days later i offered them some market shrimp, which they ate reluctantly, and a few days after that i offered them some frozen krill and they ate that, though not as enthusiastically as i had hoped they would. so i gave them a few days.. and i decided to try the massivore that came with the fish i put in a small handful, maybe 20 pellets max. ALL of the fish ignored it completely, it went to the bottom, disintegrated and fouled the water.
i still have most of those fish.. lost one to starvation because she quit eating about a year after i got them (she was blind when i got her, i think she did amazingly well for a long time). and i accidentally sold one, i had intended to keep (another long story you don't need to hear). but the rest i still have 3 years later..
i'm NOT new.. i've cycled and started MANY tanks. i know what i did and when i did it and nothing that i did could have caused the cloudiness or the stink. there was no leftover food from previous feedings, the gravel, as i said before had been completely cleaned just a few weeks before, and there was no leftover food from the two previous ill-received feedings.
i'm not going to explain myself any further, i'm NOT the OP on this thread. i offered my one and only experience with massivore for their reference, not to be questioned like an idiot by children.