I was going to mention a wave maker but when I looked at what was available on Amazon I wondered about whether it would be too much. When you say "small wave maker", how small do you mean? How much water does it move? Most of the ones I saw started at about 500 GPH and went up from there. And only when you got to about the $50 price point did flow controls enter the picture. That made it look like the choices were raging torrent or spend more than what another HOB would cost, which made it a less than attractive option. If I'm overestimating the impact of 500 GPH of water movement or have missed some less expensive options for control, I'd really like to know.