Without a tester there is no way to determine the pH.

www.discounthydro.com has the best pens for the best price...in my opinion.

If there is a Worm's Way near you, or any hydro store, they have them.

pH is so critical that to water without it in an indoor setting is asking for failure.

Outdoors has a lot of environmental elements that will buffer the water naturally. Indoors does not.

Get a pen.