Here's the data sheets I found on the Stratus pumps from the KLC25, to the KLC120...
https://easypro.com/wp-content/uploads/2017/09/KLC-SpecSheet-All.pdfThe largest two pumps they show (KLC100 and 120) would be candidates for using 3 or 4 diffusers at 4 foot deep (thereabouts). I know nothing of this brand, by the way. Should you want to go deeper with one or more of the diffusers (like 6 - 8 foot), you should consider reducing the number of diffusers. The max number of 4' deep diffusers would be 4 to 5 respectively. Otherwise, you start under driving the diffusers, not a big deal, but not optimal either.
3-4 diffusers will help with floaties, but the key word is "help". They will not eliminate normal floating films. Just an heads-up for expectation purposes. My diffusers will keep a 10 to 15 foot diameter of nice reflective water for each diffuser. The space between them still has floating films (or worse sometimes) especially during days without rain or wind.
When you check your pond water temps...start at the deepest part. Might as well take readings about every foot as you come up (you're already out there - might as well, the collected data might prove to be interesting) and see where the temp starts to change. You will find that the topmost 5 to 10 inches can be drastically different depending on time of day. For comparison purposes...compare the very bottom to 18 inches from the surface. Above that could be misleading. You are looking for a small (1 to 5 degree difference) from the very bottom compared to about 18" down from the surface.
Diffuser lines at 5/8" inner diameter will be best for your area of the pond and 3/4 to 1" inner diameter from the pump to the remote manifold. This size depends on how far the pump is from the pond/remote manifold. AND, you will want the 5/8" line that is in the water to be weighted so that is sinks. Most folks that have tried to sink the more affordable line options with creative ways have had a "fun-time" keeping it down, or more importantly bringing it up and putting it back down for maintenance/repairs, and ended up switching to weighted line in the long run (At least the few testimonials I have read here at PB). Get the weighted line.
