with eggcrate you build it so its short on the sides and front so that you can fill between the eggcrate with gravel or w/e you chose. You need to cover the eggcrate in window screen or some kind of substrate barrier so stuff don't go through it and get under it. I fill in around with gravel up to the top of the eggcrate, then use window screen as a barrier, then put on my substrates. only place you can see the eggcrate is from behind the tank. I do it like that so if i did want to see under it i can.

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