I have been wanting to do this for a while. This is a rimless 6 gallon tank. Substrate is ADA amazonia regular and ADA Bright sand. I also use Ohko stones. Lighting is a 28 watt coralife aqualight 10,000k bulb. Cave is made out of steel mesh encased with waterfall foam. I am planning on putting some Apistogramma Borelli's into this tank. The dimensions of the tank is 18x8x10.
Picture inside the cave
Final after running a diatom filter for about 20 minutes