I made this growing box for my seedlings and intent to keep them in there until they are about 6-8" Then they will be moved to a room with an 400Watt HPS to complete vegging and to let them flower. For ventilation I used 2 3.25" computer fans. I can control them (fan speed) by changing the voltage. The fans are extracting air. I desinged two air ducts (no fans installed there) so the fresh air gets sucked in and enters the cabinet on the bottom. (the ducts are "mazed" so no light gets in through them) Note that these are the only opnenings in the cabinet. I want to put about 4 seedlings in it. In operation the cabinet gets about 80 degrees constantly. If it turns out I run out room too fast (I'm concerned about the height, it could get a bit tight when the plants get big) I can always move the top up with a small modification. The cabinet is made of glass, it's my old aquarium. Inside I made it all white with paper. On the outiside I put carton to block the light from the outside. What do you guys think? Any suggestion are always welcome, I might have forgotten something. Note: the sizes of the components (fans, light, air duct) are not realistic. Just made the drawing to show what I mean. Also on the pictures the lights seems to block the airflow, it is not in the cabinet, fans are not obstructed.
instead of putting it all in an aquarium.. you could just as easily use a cardboard box... no shame in that... and as for the height concerns just gently bend the plant over and stake in to the doil using an unbent paperclip in a U shape...