Rainbow Shark W/ Eel And Betta

[Hunterprey]

Hey Im thinking of adding a Rainbow Shark to my 50gallon 48 X 12 X 19 Will it get along fine with my Half Banded Spiny Eel and male Betta.
Will the size of the tank be enough to avoid problems.
I picked rainbow over RTBS (I prefer the RTBS) coz I read somewhere that they're suppose to be a bit less agressive than RTBS,
Is this true. There's a few hiding spots in the tank.
Thnx in advance.

 

[fifefish]

Sharks and Bettas don't mix at all...

didn't even know eels could either

 

[Hunterprey]

Thnx I had RTBS and Male Betta together b4 in a 20 gallon, 2 ft long tank.

Betta was almost 2 inches and RTBS was like 3 1/2 inches, they did fight, Betta was actually more of the agressor and held his own against the RTBS. I was just wondering if the agression will be lessen/just ignore each other in a bigger tank since they'll have more room to establish they're territory.

Anybody had luck putting these fish together in a big enough tank? Im not as much worried about the Eel coz it will outgrow the shark, however, the Eel is not really agressive and the shark might take advantage of that.