Advice / Instructions for a Bottom Drain

Hi

Planning on constructing a new pond with a friend at his new house. Basic
plan is 6000ts, concrete lined with a bottom drain. Edges will be raised
60cm or so.

Can anyone advise on any good sites etc with instructions on what's needed
for the botton drain & some installation and construction guidelines?

We're pretty sure we know what we're doing but would like some information
to make sure!

Thanks