That's nice, I think the water fall will add nicely to the pond, if you dont make it too high, I think it'll make the water appear more (does that even make sense?)
Anyway, have you ever check your amonia level? I'm wondering if with just plants, will that be enough to absorb all the fish waste. Well i'm pretty much comparing it to my indoor tank but I should be comparing it to my pond (small too)!
I'm wondering how it would be without all the bio filter. I'm guessing that it should be fine for quite a while since my pond only have small waterfall filter and it was enough for a whole year with my fish load (should be similar to yours if counting the big fish = severl small fish) and I also had guppies in the pond in summer.
one of my friend have a lotus tub (probably about 1.5 feet in diameter) with most of the tub filled with clay and whatever else, leaving only about literally 2-3 INCHES of water and she has like 100 guppies in there, every inchs of that tub are covered with guppies, pack and they are totally fine, been like that for a few years and she had nothing else but the lotus and guppies (well, and clay) it's a wonder, really, how the guppies survive that and there are all ages in there, beautiful healthy looking ones too.
back to you, there is solar air pump out there. I bought one but since I dont have much sun it's kinda stupid to even own one so I retured it. but it worked great when there's sun. May be you should check it out, so it doesnt have to take anything away from your house
Just want to add that I love that purple plant!!