Problems with watertank effects and ink drops.

Hello!
I am planning on releasing a toolkit fairly soon, but I'm running into some problems. I am filming some ink splatters, and then trying to key them out. However, around the edges of the ink, there is a wiggling. This is due to the keying. Is there any way to fix this? Because it effectively makes the clips unusable. Should I use a Matte Choker or something?


My second question is, how do I film a watertank effect? I have a fishtank that I am using, but it's not working out so well. I'm having problems extracting the ink. Any tips?
Thank you so much
Kai

Golf is a good walk spoiled
~Mark Twain