"MartinOsirus" wrote in message
...

Be careful about using a system 1 diatom filter (don't) on smaller -
like 20
gal
tanks. The excessive flow creates a crurrent that stirs up the gravel
bed and
releases dissoved organic compounds that kills the fish. This is what
happened
to me. There is no warning I'm aware of that comes with the filter.

If excessive turbulence was the catalyst to release sulphide gases
trapped in the substrate (it wouldn't be DOCs which would kill quickly),
then wouldn't your advice be applicable to any pump or filter?

If this happened the way you described, then there would have to be
considerable detritus left in a rotting state for a significant amount of
time. This points to maintenance issues.

My understanding is that a diatom filter is a poor choice when there is a
lot of particulate matter, as it clogs the diatomite too quickly. This
filter is a water polisher, but the fatal combination seems to have
happened when it upset the rotting detritus in the gravel. This
occurrence might not be realistic to warn against. I apologise if I'm
mis-reading your post.

NetMax