[puopg]

cant you use like a transparent suction cup and more bouyant material + stone such that the stone does not 'collapse'? The suction cup can merely hold the stone in place to prevent moving. If the hardscape, what ill call it, is bouyant enough to stay afloat, then the suction cup which can easily be hidden behind should be able to hold the piece in place. Obviously if too high current or too large a surface area being perpendicular to the flow of water this will not be enough to hold the hardscape in place.

Potentially even use magnets? Like those koralia powerheads