Two T5 Lights 15W-Good Lighting?

[LicianDragon]

I have a 20 gallon tank with two light fixtures. The bulbs are t5, both 15 watt. One is full spectrum, the other is flora-glo. I feel like this is low lighting for my tank and I would like to at least have "medium" lighting for my plants. If these aren't strong enough, what sort of lighting would be? And can someone explain the difference between t5 t8 and t15 with lights?

 

[Ps3Steveo]

Some are more powerful than others, they give greater PAR, the T5's you have give you enough light to grow anything really with good flow, nutrients and CO2 etc.