Any theories on why my fish use only a fraction of the tank

This has been going on for so time - all the fish except the rainbow shark and some tetras spend about 80% of the day in less than 20% of the tank space ! The cluster in the one corner and hang out. The dominate male rainbow goes out and makes a lap every once in awhile and the Gourami comes and goes ..but hangs there allot. I have moved/change decors and plants in that corner. I adjusted water flow to see if it was something with that … nothing seems to change this behavior. My other rainbows us the whole tank ….anyone with a thought what am I missing.

 

Couple wild guesses maybe they like that decoration below them or maybe they like bein at the return side of your filter Incase anything tasty comes out their first to grab it… big maybes…. Do you have floating plants on that side of the tank or all submerged plants. Nice looking tank!!
Edit could also be the flow from the filter is a little strong seein their to the left of where your return is. Just another guess

 

Maybe the bright lighting required for the plants is contributing to the shyness.
It's usually a good idea to arrange the decor as to allow a defined open swimming area at or near the center of the tank.
Maybe the Shark is intimidating the tankmates.

 

Couple wild guesses maybe they like that decoration below them or maybe they like bein at the return side of your filter Incase anything tasty comes out their first to grab it… big maybes…. Do you have floating plants on that side of the tank or all submerged plants. Nice looking tank!!
Edit could also be the flow from the filter is a little strong seein their to the left of where your return is. Just another guess

thanks For the reply! I have had floating plants on that side, the ship was in the middle a few weeks ago I swapped places to see if they were clustering around the tallest decor. I also have covered up the side wall with the same rock panel that in the back makes no difference. The food idea is interesting there are two “collection” points the far corner and that one. The far one is much bigger and the gourami does go over and suck the top of the water lol could be related.
t

the lights do not stretch all the way to the edges so each end is semi shaded … I’ve considered more floating plants for sure. I have had the middle more open (swap ship for rootstump thing in photo. And the shark does not hang out but when it skims over the decorations are plants in the area only, the Gourami reacts (fins up and out) and those two will chase mostly shark being chased. The shark will occasionally chase the male rainbow on his lap so Could be just strait intimidated….

also seems like maybe the male rainbow is “ herding” the females back ….just odd cause my other rainbow have a dominant male but not this type of thing.

thanks for thoughts I will,keep,observing. Maybe the shark…

maybe a new male, to challenge ..the
Other… rainbow …no no.No Lol.

 

Don't have anything constructive to add, but I just wanted to say awesome tank, and I just LOVE that shark!!!!

 

In my tank my CPD's usually hid in one corner of the tank that had more wood and plants than the rest, which I'm pretty sure they did this when they were stressed in order to hide. They were new at the time, so any disturbance led them to hide in that area. Now they're a bit more comfortable and are starting to spread across the rest of the tank, just really slowly.

 

This behavior is commonly seen if one fish is territorial.....probably the rainbow shark as they are notorious for being bad aquarium companions

 

Maybe put shark in temporary QT and see if the other fish's behavior changes.

 

Don't have anything constructive to add, but I just wanted to say awesome tank, and I just LOVE that shark!!!!

Thanks ! Shark is cool fat and happy - just its presence may be an issue but behavior it’s pretty chill.

Maybe put shark in temporary QT and see if the other fish's behavior changes.

I’m thinking of moving it for sure just to see. After about 2 + hours of observation I found the shark initiated chasing 2-3 in an hour the same actually as gourami basically. At many other time the female rainbows will scout the bottom right next to it. The gourami ans shark were also most likely to chase each other. If the rainbows are reacting to the shark it’s not based on specific aggression that I observed, not saying that’s its just living there may be enough,

The male Glossolepis dorityi is The Main culprit in that in the time I observed he was nearly continuously herding any-other rainbow that leaves the corner. If a few get past then there is a few minutes of everyone swimming around until eventually they all regroup and he starts making laps etc. there are at least two (third is big female or very submissive male never see fins up) other males of equal size and one smaller. The 5 confirmed females are all Glossolepis dorityi with one possibly two Australian females total assumed is 7 females 4 males ratio.

My theory is that as the only Glossolepis dorityi male and the majority of the females are of his species he is asserting dominance possibly “protecting“ from shark by keeping them tight together like that. The big Not dorityi female (added picture cause she is sooo pretty) is the most likely to “get away” and start a s group ”escape” or free swim. i don’t know where to move shark as my hospital tank has fry in it and so does one of my bigger tanks. My angels would hate it and the other tank has Bosimani rainbow fish that have orange so Might make real aggression lol!

for no I’m going to keep observing then move shark if I can, I want to move the “mixed Australian“ bunch but until fry grow up everyone is kind of stuck.

many thanks for the thoughts helped me when watching tank - yes I sit way to long in front of them. PS i also caught (someone mentioned bright light) that might light was Cranked way up for part of the afternoon I must have messed with settings and not change back.

many thanks again !

pretty sure it’s a girl .. so pretty but also one of the largest in the tank.

 

R sharks can be the biggest jerks in the world. Beautiful but jerks lol

 

I’m really hoping that’s not it but idk .. the male is keeping them in the corner but the rainbow shark may be the reason I guess. I haven’t posted yet but I’ll be adding two tanks was a big sale and … anyway I now have some places to start thinking about moving things around. Think my 20 cardinal and 6 white skirt tetras would do better with shark in 40 breeder ? If it has to it can have a 30 to itself in a spree weeks.

 

so little update.

I trimmed all the plants down low across the front and removed the tall hard scape feature on right side of picture (white roots with wood sticking out).

they still congregate but not nearly as much. Now if I could just control the bb algae sigh lol