[jschlosser]

Before I move ahead with this, I want to check with you all to see if there is something wrong with this idea. I am wanting to establish a large clear area in the tank with a large piece of slate covering about 1/3 of the substrate. The tank is 15 x 55 inches and I am expecting to cover about 12 x 18 inches in one area. The rest of the tank will be fairly heavily planted. Is there any problem with the lack of circulation beneath the slate slab?

Would a better approach be to build up a solid "rock" - layering pieces of slate and sealing them together with silicone - with no substrate beneath it?

 

[ladyonyx]

A full slate slab would be fine, but as you pointed out, more water flow might be better. Maybe you could just put an aggregation of large gravel underneath the slate slab so water can flow more easily under it

 

[jschlosser]

I ended up leaning it against the side of the tank at an angle with the filter intake next to it so it gets plenty of flow. I was more concerned that I have a place to pour in new water without worrying about erosion/disturbance of the substrate than anything and this works. In fact, it gives the loaches another hideout.