By no means am I an expert. Long story short, I live in NY. 3,000 gal in-ground pond 4.5 feet deep covered with a heated greenhouse. 1st winter with the greenhouse. around 40 channel catfish. Five 4'x8'x12" grow beds in Hydrocorn media (baked clay). thought my 80,000 b.t. u. ceiling furnace would keep my water temp warm enough. No way. water slowly approached 49 degrees F. noticed fish were backing off eating and my plants started slowing in growth. tomatoes were dieting off. 0ppm on everything. I took emergency measures and installed a 50 gal. conventional gas water tank. water heater brought the water temp gradually up. fish are eating like starving sharks and my water is 80 degrees. again, my bio filter is 0 on all readings, plants not growing like they should. I assume I lost my bio-filter when the water got into the 40's so I need to re-cycle with my catfish in the pond. Its probably me and not Mrs. Bernstein's book but to me it seems the book focuses more on fish less cycle. can anyone give me guidance in re-cycling my water (bio-filter) with fish? I hate to lose any. their getting to be a nice size. Thank You! Happy new year!
Here's a good article on iron deficiency: