Attention - this is a prototype! 

I wanted to develop my own version of a shrimp shelter, fixing the errors of popular models. Community ideas were taken as a basis and improved:
Sharp corners have been completely removed.
90-degree angles were removed, and smooth curves were added for better water flow.
Wall thickness is 2 mm on average - this is more than enough for aquarium pressure, and it also saves filament.
The entrances are oriented towards the direction of the filter's return flow for natural water circulation.
Slots have been added to minimize water stagnation.
The project includes modifiers for creating Fuzzy Skin. This increases the surface area for the growth of biofilm - the primary food for shrimp. If you do not need this, simply disable the modifiers.
It is best to print from high-quality PETG plastic, as this reduces harmful emissions into the water to zero. I will be glad to receive feedback, as I want to make a good home for shrimp.
P.S. So far I only have Danios living in it and they use it as a maze
P.S.S. After 3 weeks, shrimp took over.