How to deep clean 80 gallons AIO tank?

[vijay_06]

I picked up a used Innovative Marine SR Pro 2 80 Gallon AIO aquarium recently. How can I deep clean the tank? The display area seems not too bad to clean, but the sump area has a lot of deposits on the walls and the floor area. Seems like crushed sea shells and sand particles. I am wondering how to get all that cleaned and sucked out front the narrow sump area.

Please see attached pictures.

 

[Catawba_Valley_Reef]

I would use a shop vac and vacuum the rear out. Then fill the tank with tap water and mix in some citric acid. Let it run for a day or two. Make sure to rinse well once you dump the citric acid water.