If you want to find fish condos than I would suggest an Side Imaging model unit. There are a lot more expensive though and a little harder to learn to use – but the upside is that you can look at a much wider area of water in one pass with one of these and mark any interesting looking spots without having to run over them.

The 581i replaced the older 580 units so anyone with one of those should be able to give you feedback on what they like/dislike and how well it worked for them. I will point out though that the 581 uses the wider 83kHz 60 degree beam for showing Fish ID Symbols only. This is a restriction in the 500 series units. To see the actual sonar returns from this much wider area you would have to go to a 700 series unit. The 700 series units will allow you to show just the sonar information from the narrower 200kHz 20 degree beam, just the wider 83kHz 60 degree beam, both combined or both side-by-side.