Bubbler
Borosilicate Glass Tubing, 1.50, ebay
Borosilicate Glass Tubing, 10mm OD, 1mm wall, 5′, 100 pieces, SS10 $67.
Borosilicate Glass Tubing, 10mm OD, 1mm wall, 5′, 72 pieces, $55.50
85% sugar solution matches index of refraction.
Oil close to index of refrection.
Extruded plexiglass, 3.75″ ID x 6′, $111.
Exruded acrylic, 5″ ID x 6′, $21 / ft.
Plan
45 12mm od tubes fit in a 4″ ID tube, 100 fit in a 6″ ID tube.
Bubble from bottom, have a pressurized chamber, slide open door w/ nitinol wire / spring.