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I now have in a 350cm*100cm*80cm

1 Megalodoras
1 Marmoratus (leiarius)
2 Royal Panaques
1 Leopardus Pleco
2 Gibbyceps

was thinking of adding
2 sorubim lima
and
1 Juruense

would that work ?

IMO, no - your tank isn't wide enough & doesn't have the footprint to adequately cater for all those bottom-dwelling species together. As a basic guide a tank should be twice the width & 4 times the length of your biggest fish (adult size)

if Leiarius gets to 100cm TL approx, the footprint should be 400x 200 cm (as a quick example)

size not counting; both lima and juruense are much more mildmannered than Leiarius

with lima a fairly gluttonous feeder, but Brachyplatystoma can be quite fussy, and many starve to death when acclimatizing due to foodcompetitors

if you like more fish, get some adult Myleus (8" or more), highbuild sturdy characins.
their active swimming behaviour will draw he catfishes out of hiding and unlike Pacu, Myleus doesn't outgrow this tank.

they are large enough and round enough to be safe from the Leiarius.
best get 8 or 10 or so, it's a true shoaler, but very mild mannered.

other great fish would be a few adult or subadult Oscars (Astronotus occelatus), or Hypselecara temporalis or Uaru.

Was thinking of getting the Leiarius in another tank

cause as you say it will outgrow my biggest tank now...

Was thinking bout getting a RTC or 2-3 in a new tank i am bound to setup (500*250*140)
but might also be very nice sight of having my Leiarius in there with some friends... and no RTC

Whilst that is a very nice size tank, it's actually just a bit short of large enough to hold a RTC for life. It is probably better to stay with the slightly smaller fish.

--
Mats

Well can't get them any bigger
or i'll need to start diggin and that i won't be allowed( wife)

I could perhapz keep some motoro's in and some leiarius sized catfishes