Bill Stock wrote:

The Nitrates in the existing tank (75g) range between 40 and 80+,
even with
weekly 50% water changes, reduced feeding and gravel vaccing. The big guy
(girl) must be close to 9" now and has a fair girth. I'm hoping the
increased water volume/flow in the new system will let me keep it below 40.

21 grams of crap in 140 gallons comes in right around 40 ppm. Looks
like you'll meet your goal with a lot less work.

Thanks Altum, I'm a little surprised that it's 21. I had expected higher.

Hope I solved the diffeq right! I'll be really curious to hear how the
actual measurements turn out.

Have you considered putting a cheap flourescent shop light over your
sump and growing duckweed or anacharis to lower the nitrates? You could
even harvest duckweed and feed it to the GF (mine love duckweed).

--
Did you read the FAQ?
http://faq.thekrib.com