I posted this in fall:

Jo Ann supplied the following observation and experiment she's been
running. Remember that this is a single incident AND it is in a tank.
This does not necessarily mean there are not unknown factors at work or
this applies to any other tank, pond, water pH, condition, etc.

1.5 mo ago she super sterilized a tank prepatory to moving fish. Unknown
to her, Steve had put a small amount of Micro lift (an organic waste
remover) into this tank to see if it would help reduce the ammonia levels
of these fish when they started spawning. The stuff had been sent to them
to try out.
The first thing she noticed was that peroxide did not clear the purple
sterilizing level of PP in the tank.
She then dumped all water, changed media and cleaned the gravel. Steve
added a few more drops of Micro lift to the tank (without telling Jo Ann).
This is classic example of a blinded study cause Jo Ann sure was in the
dark.
Jo Ann put in the fish. Soon she noticed the fish were lethargic and the
physical showed that the gills were liver colored purple. She immediately
checked the water parameters but the ammonia was not bad. She did a water
change anyway. Soon the fins were shredded and she moved the fish to fresh
water, did scrapes and found nothing. Some of the fish died, others
recovered after being moved to fresh water.

She dumped all the water in the tank again, left the media. She left the
tank for 2 weeks with no fish and then tested for ammonia which was now off
scale. She did another super PP treatment and once again the peroxide
wouldnt remove the PP. ONce again she dumped the tank, left the media.
The next day the ammonia was 0.1.

2 weeks later fish came in, put in the tank but didnt check ammonia in the
empty tank. 3 days later the fish were spawning and the ammonia was off
the charts. She did a 50% water. 3 days later the fins were shredding and
on the fish were on the bottom and lethargic. A scrape showed nothing,
gills were purple. The fish were moved out of the tank. Some of the fish
died, the rest have neural damage and probably wont survive.

She did 2- 100% water changes on the fishless tank, but the ammonia was
still off the wall 24hrs later. Did another 100% water change on the empty
tank, AND replaced the media completely and found ammonia at 0.1 later that
evening. Steve now told her he had added the Micro lift.

Jo Ann is planning on adding some experimental fish to this tank in the
future to see just how residual the effect is going to be.

Note: The bacteria in the Micro lift is purple bacteria. Some species of
purple bacteria reduce nitrates to ammonia. Also, purple bacteria eat H2S
and so are sold in an H2S formula to keep em alive. All additions of
Micro lift were less than the recommended dose. Jo Ann has acidic water,
adds a calcium buffer to the water and salt. This was the only tank the
Micro lift was added to, no other tanks of fish (with no Micro lift) have
these symptoms.
Ingrid