I'll kick it off.
-I've always wanted an activated sludge nitrate/phosphate removal system that could fit under a tank. Bye bye biopellets and GFO!
- a cheaper alternative to those uber-sexy Vortech powerheads
- cheap tank automation
Things I can offer to other members (if I have time

):
Chemical, mechanical and electrical engineering. Specialize in water treatment, UV disinfection, LEDs, semiconductors, fluid dynamics, automation and control.
Product design and prototyping. I have CNC mill capabilities at home for small parts smaller than 8"x 6" x 6" (particularly acrylic and aluminum) and have access to bigger mills if necessary. Can 3D print PLA and ABS parts and can injection mold silicon and urethane.
3D modeling.
Let me know how I can help!