Nitrate Test Kits / Fertilizers

Fellow Aquatic Plant People,

A thought conceived last night while testing the tank:  An "undetectible"
result in a nitrate test should always be verified by adding a drop or two of
nitrate containing solution (such as PMDD) to the test vial before you dump
it just to be sure that the reagents were active.  I've noted several false
"undetectible" results with a recently purchased Wardley kit.

 A question:  What is a good solid fertilizer (brand names and/or sources,
please!) to add to the substrate to complement PMDD?  Right now I use Tetra
Crypto, which is very $$.

An observation in need of diagnosis:  My hygro polysperma seems to be
dropping more leaves than usual and the corkscrew val, which is otherwise
booming and sending runners all over the place, is showing clear, yellowish
tips on some of its newer leaves.  The tank is still recovering from a major
crypt meltdown due to an increase in lighting (45 to 60 watts, better
reflector.  Man, can those crypts melt when the light increases!).  Am I
experiencing a deficiency in nutrients?  Macro or micro?  Algae is

Tank specs:  20 gal / pH=6.9-7.2 / NO3<5pmm / T=80 degrees / 13dKH, 12dGH /
60 watts full-spectrum flour. / 1.5 ml daily PMDD (for last three weeks) /
DIY CO2 / Fish load:  4 platys, 2 SAE, 1 Cory, 5 Rasboras

Thanks for any advice.

Bill Cwirla
Hacienda Heights, CA