im buying a new 4x2x2 fish tank for my room and i want to keep predatory fish in it, i like the redline snkaehead but they grow too big, i like active fish that swim alot eg exodon. but they are hard to find in london, i've kept cichlids mainly over the years and have a pair of dovii in my other tank. so i want sumthing different and fun to watch and deadly.... what u guys suggest?