Marine Betta and Blue Hippo Tang

Hello all;
Does anyone have any experience two different fish types that seem to like each other?
I have a Marine Betta....he's been in the 90 gallon tank for almost 3 years and I have a newly added Blue Hippo tang(in the last six months) . Anyway, these two seem to really like each other, but only when the tank light comes on in the evening. They rub against each other, swim together, etc..., but lately I've notice big bites out of my Bettas tail and posterior dorsal fin.
Is the Tang doing this? It grows back and he doesn't seem stressed at all, but I am. :-[LOL
The only other tank residents are two Percula Clowns, who have been in the tank for 4 years and a Skunk Shrimp.
We also have snails, crabs and one of our crabs is getting huge and took up residence in a really large decorative shell I had in the tank. Could the crab be the culprit?
Thanks for any help or thoughts someone has on this.
Marinegal

 

That's really cool your hippo has made a buddy. Mine always was real skittish, and would spend most of my viewing time in its hidey-hole, which seems to be common with them.
I agree that's its probably not the tang. If it wanted to pick on the beta, I think it would most likely use its spines, and you'd be seeing puncture marks as well.

 

My hepatus has never had a problem with my betta, either. I think it's a crab, you know how much bettas like to sit on the sand. Here's a picture of mine staring at me from his "home" (a large tank ornament)

 

Thanks everyone....I was hoping it wasn't Dory LOL It's really neat to watch these two fish interact with each other. I would like to get rid of the crab, unfortunately I'm attached to the shell he's in. Long story. I'm trying to figure out how to put his picture in here.

 

Couldn't you take the shell out and get rid of the crab?

 

Yeah, well, I really didn't want to kill the big crab. Still can't figure how how to post pics in here

 

take the crab to your LFS, in my opinion, people who think its a nuscence to take unwanted animals to better living quarters shouldnt be in the hobby...

 

It not that it a nuisance, Its a freaking hermit crab! Most LFS I have ever been in would laugh straight to my face if I brought one in the them..

Put the Crab in a blender (without the shell of course) and feed it to your tank after a few pulses, they will love you for it....

Sorry but I just couldn't resist! LOL... If you really that worried about the crab find it a bit bigger shell, put it in a bowel with holes in it and float it on top of your tank. Give it a few days and it will change shells, this is a guarantee, they like bigger and better.

 

ahh, i thought it was a different crab...im just so sick of hearing people toss out really cool animals like mantis shrimp and fish that are herassing things, like there trash, i used to keep mantis's and they where by far one of the most intelligant species ive come across.