I've kept 9 - 12
D filamentosus in heavily planted with wood/rock scapes (forming hollows/crevices), fish were sourced in very different places, some years apart, both projects began with small grey fish
The 1st group comprised 4-5 males & 5-6 females - they formed a distinct school configuration & patrolled the tank as a group, as the fish matured, there was minimal aggression, even when they began to spawn, the group dynamic remained. While there was an apparent hierarchy within the group, I never saw anything approaching a "fight", some posturing/flaring but no physical damage.
Fish were smaller than the Seriously Fish species report, & stunning to look at as they matured (unfortunately I never took any photos)
Local tap water was the sort that produces a good "limescale" with tank pH ~6.8 (CO2 + substrate effect as tap was pH ~7.5), I had these fish ~18 months before losing most of the tank after an apparently normal water change - nothing measured out of the ordinary but there was a local crew working on a nearby water main ... so like Darrel my experience ended in tears (I tore the tank down & set up Tanganyikans)
I kept looking for another chance with these amazing fish (which led to group 2 finally)
The 2nd group was also quite balanced in male/female ratio, but this group never formed an interactive shoal, they might move in a group at times but behaviour was completely different (boring in comparison), the females were very secretive, the males more visible - the females could be quite nasty to each other & to the males; males did some sparing as well - I could glance over & often see an apparently empty tank.
There was considerable size range within each sex with the dominant fish being significantly larger (previous group was much more uniform in size/development)
I tried removing some fish, placing different combinations in various tanks ... finally I just traded them on after a year or so
Unlike the first group, there was little spawning activity, they went through the motions a bit, but nothing really definite; this group was physically larger, & less colorful than the first.
Local tap water at this time was very soft, pH ~6
Both groups were listed as wild caught with no location information.
I didn't find these fish difficult or particularly sensitive (though I'm a frequent water changer), they ate frozen food, flake, micropellets (I pre-soak any dried foods for a few minutes) - if I started with 10 juveniles, I still had 9 or 10 a year later BUT I seldom add fish to a tank "community" & quarantine any new additions.
Other tankmates were some upper level schooling fish (small rasboras, tetras etc), otos, some shrimp (that 2nd group was rather hard on the shrimp population
)
If you pick up a group I hope you post photos - perhaps the Wet Spot has source location details
