Interlocking Lambda Phage Cro Repressor Protein and DNA
Description
These are two molecular models of a lambda bacteriophage Cro protein and a region of DNA to which it binds. As long as this protein is bound to DNA, the phage will remain dormant. Stress triggers degradation of this protein and re-expression of the phage.
Instructions
The narrow towers don't quite print right on my bot, your mileage may vary. I wish I'd made them every so slightly smaller so they fit better, or had some sort of sand-blasting polishing tool.
License
All Rights Reserved
Interlocking Lambda Phage Cro Repressor Protein and DNA by mrule is licensed under the All Rights Reserved license.

For a fishtank, I would suggest openings in it that would allow a small fish to escape a big one.