Update:2021 Please read this
https://forums.thinkfish.co.uk/fishtank-filtration-and-cycling/replacement-for-jeyes-kleen-off-ammonia-hydroxide-for-filtration-use/I've just helped a neighbour (new to fish) who had followed my advice and has started to complete a fishless cycle. They called to night asking if i would check their water etc and see how things are progressing. Well i tested the big 3 and all coming in at zero. I tested again still zero... confused.
I got them to tell me what they had done - all ok, adding small amount of Kleen Off, using a filter start etc.
I was really confused until in caught a glimpse of the Kleen Off, it was for sinks and drains and was SODIUM HYDROXIDE not amonia,. thank god no fish were involved.
Anyway emptied the tank, washed the substrate, soaking the wood and rinsed stones. Have re-filled the tank and starting again, hopefully all that is lost is time.
Might be worth bearing in mind when advising new peeps about cycling - there is more than one version of Kleen Off. I would hate to see fish getting burnt.