Discovered a little tiny bug, threw it in the toilet, no pics but inter. in control

So I got some fish emulsion yesterday, put a little in some water and gave it to the plant. Woke up this morning and there was this little brown flea sized beetle looking bug sitting on the thick part of my stem. Dont have pics so I'm not looking for identification...
I'm looking for prevention of bugs and how to check for more signs of bugs. This Is a first time clone grow and ill be damned to have it go down to little pests.

I'm new to this but I'd understand some bugs would lay eggs on the leaves or leave a silk web residue like with gnats and I don't have any of that. Either way I have about 10 days before anyhing would start becoming an infestation. So best course of action for prevention? Thanks in advance guys

Best course of action is using something like Azamax once every week or two during veg; you can also mix in some diatomaceous earth and neem meal into your soil in the future.

I think I had an aphid. I was looking through insects and although some of these are green, this one was brown. I believe it was an aphid.