new vfx not working in game and breaking the original

I'm trying to create new fish for the fish tanks. I have managed how to work out everything but changing the VFX in the game. Once the fish are placed in to the tank they become VFX, I have created new VFX for my custom fish and in studios I replace the name of the effect under "aquarium" with the name of my created effect. This is were I am confused. When in the game I click on the tank and click "add wild discus" which is the custom fish I created it takes the money but does not appear in the tank (it is in the inventory of the tank) the strange thing is it also does the same for the normal discus now too. I can't work out why changing the code on a custom mesh would effect the original one in the game? I'm obviously doing something wrong but no idea what and I can't work it out.