While its usually agreed on that rocks in the bottom of a loi or GF
pond is not a good idea, its strange that rocks in a sal****er setup
is good, and bio balls are not desireable in the filter, but its the
trend to remove bio balls and filter type mats and just put in more
live rock rubble in their place........I probably has to do with the
type of rocks normally used in SW setups as compared to what is used
in a fish pond........I wonder how long its going to be until LFS //
Pond Suppliers etc start selling "Live Rock" for koi ponds.

In sal****er, particularly reef tanks, nitrates are a problem. Nitrates
form particularly well with bio ball set ups, hence these are starting
to be not used in sal****er tanks.

As for the substrate, one thing about ponds is that they tend to have
lots of external stuff (example, leaves) getting into them. This creates
a maintenance issue.

One can have the same issue in an aquarium... but the bottom is smaller.


C//