The last one is good for me LOL especially if they are just fry.
You might train the cat/dog to sit next to you and just eat them off the floor!
Best way to cull them is to scoop some out with a small flat net and then flick the ones you like into a tank just below you with a baby net the size if a teaspoon. Dump the reast into a bucket and flush em.
You must be ruthless as in most cases you have 500,000 plus fry to cull in the beginning.
As you move upward in size you can try throwing them into a bucket of ice water. This kills quickly and with little pain.