Hi, 

It sounds like you have fungus gnats. Periodically rinsing off the foliage can help suppress mites but keeping the actual soil damp runs the risk of over watering the citrus plant since they like to get fairly dry between waterings. This is probably the cause of the fungus gnats since they breed in moist soil. The link provided will give you tips on how to suppress them. If they are an annoyance you can't seem to get rid of you can try a Bt soil drench as described on the page, but letting the soil dry should kill the larvae. Using a sticky trap or small dish of vinegar near the plant should help trap the adults as well.

You can also refer to our webpage for diagnosing indoor plant problems for future issues. 

Our page on Growing Dwarf Citrus may be helpful to you as well for tips and guidance.

Let us know if you have further questions on care. 

Emily