Lovely simulation. Just a few observations and suggestions for behavioral changes in cats and suckers.

1) Corys are unusually social for bottom-feeders. In small quantities they will often form pairs and threes which move about the tank floor together in search of food. The current behavior model has them moving solo in the mid-column quite often, which is rare in my experience. They will sometimes dart up to the surface for a "gulp of air" then immediately back to the floor, but hovering solo in the mid-column is a low-survival behavior and generally avoided. However, in large quantities, usually more than a dozen, I have seen them exhibit mid-column, high-speed schooling behavior, sometimes for hours on end. The larger the group, the more likely it is that this behavior will emerge. Years ago, my LFS had a 150 with nothing but gravel and several dozen corys in it and they were always schooling in the mid-column every time I walked in. It was really quite mesmerizing to watch.

2) Plecos are far more sedentary than they are portrayed in the simulator. They tend to stay in a single location for several minutes as they slowly scrape all the algae away. Those in the simulation are never at rest for more than a few seconds. I realize this may be a design choice since non-aquarists are unlikely to be aware of this fact and could easily get bored with them.

3) Pure bottom-feeders should not exhibit the "pecking" feeding behavior, especially on vertical surfaces. The reason for this is self-evident. However, some of the smaller cats (especially corys) will frequently "circle dig" for bits of food stuck in the gravel.

Keep up the great work. I have this simulation running all day in my office in 4K on a 55" HDR on the wall behind my desk. Everyone who sees it for the first time is amazed. Pretty sure that TV has sold a few copies. :)

I will be quite happy to buy some DLC in order to keep development alive and I'm sure I am not alone in that sentiment. I would suggest that you release specimens with more complex behavior as DLC due to the extra time you'll have to spend in developing realistic patterns. Octopi and Indian dwarf puffers both spring to mind. The intelligence of octopi is well documented, of course, but fewer people know about Indian dwarf puffers. I have found them to be highly intelligent, exhibiting strong observational curiosity about both inside tank and outside stimuli, and they are prone to monogamous relationships. Separating a pair (when one is ill, for example) will often drive them into a frenzy as they desperately try to reunite with their mate. I once had a pair that would watch everything I did very intently. If I was vacuuming the floor near the tank, for instance, they would hover at the glass, alternating between watching me and looking down at the vacuum cleaner as I moved it back and forth, as if trying to figure out the relationship between me and it. They would make fine candidates for a DLC.