Kathy. Lady Bugs will do the trick..lol

Instead of poison, why not try Yellow Sticky Traps?
Aphids are attracted to the color, and stick on a very strong glue.
Traps are reusable, but it's less expensive buying more traps, 'if needed' than Tanglefoot (glue.)

Online garden centers/nurseries and Ebay sell Yellow Sticky Traps. Toni

Hi Kathy...is the pesticide you have manufactured especially for indoor container plants? If not, I wouldn't use it at all. If so, you can call the 1.800 number on the label for some further information about your plant.

In the meantime, have you tried a rubbing alcohol and water mist? I've never used it on Calathea in particular, but I can say that an alcohol solution is very effective at killing aphids. One part alcohol to three parts water (or stronger), applied to the entire plant with a misting sprayer.

If you've not tried it, do a leaf test first.

Since aphids reproduce so rapidly, you'll need to spray three or four times a few days apart to make sure that you've done away with any stragglers late hatches. They reproduce parthenogenetically, as well as the old fashioned way....so you have to get them ALL. Not too difficult, really, since they are such fragile soft-bodied insects.