Love heavily planted tank but how do you vacuum?

You don't gravel vac the planted area, waste and gunk that settles in those areas will break down and become nutrients for the plants.

Stuff that's important to growing plants:

Lights (about 2wpg for the tank you linked)
CO2 (major factor for promoting plant growth)
micro nutrients (mineral nutrients that are commonly sold as plant fertilizers like Seachem Flourish and Kent's Botanica Micro)
macro nutrients (potassium, nitrates, phoshpates)

CO2 and the nutrient levels will be determined b your light level, the higher the light level the more critical the other factors become.

Frequent (weekly) water changes to keep maintain a safe nutrient level (some nutrients like copper can be toxic at high levels).
 
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