NQL - The diffuser will work good with your compressor. The surface boil should be noticable. If you run this continuous in your small pond I "think" it will probably end up killing your trout in the heat of the summer. Bottom aeration with trout can be tricky and it can get a little complicated in the summer months. You do NOT want to warm up the bottom water above what the trout can with stand or tolerate (my guess is no higher than 67-68F.). You may need some more advice from experienced trout raisers / pond owners who bottom aereate with trout in your climate/region with similar summer temps about the best approximate run times for the pump.
The amount or strength of inlet flow of spring water will have a big influence on warming or cooling of the bottom temps and pump run times. You should definately invest in a thermometer that can measure water temps at the bottom of your pond (discussed elsewhere in this forum). You always have to maintain the oxygenated and cool water refuge for the trout. Brook trout probably will be the first ones to show stress from elevated temps in the deep water. Also you should only run your pump/diffuser during the cooler periods of night so warming the water is minimized. I "GUESS" that you will need to run the pump about 2 to 3 hrs per night in mid-summer. At least that is where I would start. Not sure when the best time for start up in spring or summer is. It really is based on temps and DO at the bottom. Ideally you also need an oxygen meter to monitor oxygen levels at the bottom. However this is pricey ($300-$700), a high maintence item and probably out of your budget. There has been recent discussion of used / rebuilt oxygen meters that are moderatly priced.
Hopefully you will get more detailed experienced advice that what I have provided.
