I adapted a well pump filter to attach to the input to the impeller as the pre-filter. It has worked well for over 10 years despite some unusual challenges like the very small gravel in a pre-planted pot dropped in the pond by the raccoons. (The pot landed upside down on top of the pre-filter and the gravel got sucked right in. I don't buy from that nursery any more.They also used potting soil with perlite and styrofoam beads.) Regular pump maintenance takes care of most other problems. I really don't care for sponge pre-filters. Without almost constant attention they clog and put far too much strain on the motor. I use a pump and pre-filter that can deal with all but the larger debris that gets removed with a net anyway, while the water with finer particulates goes through the pump into the Skippy where it is filtered quite nicely by quilt batting.Once while spring cleaning, the pump was running without the pre-filter on the intake and a fish tried to swim into the intake and got stuck. It was not easy to remove him.

Nepeta is one of the most carefree long blooming plants there is. I think it's worth a try. I have two cats, and used to have another. None of them took any interest in my nepeta at all, even when I stuck it under their noses. We have ferrel cats in our neighborhood too and I have never seen one around my nepeta. If you do happen to have a cat in the neighborhood that wants to eat it or lay in it, at least it probably won't want to poop there too. Nepeta is easy to propagate. If you carefully pull a stem away from the base, it will already have itty bitty roots attached to it and can grow into a good size plant in one season. Just stick the new starts in a shady place for awhile until they get established. It should be very easy to get nepeta in a plant trade or make your own starts if you purchase a plant. Then if you do happen to have new cats hanging around, you won't have spent much and can rip it all out. I don't think you'll need to. In fact there may be some places in your garden where you can use nepeta as a ground cover instead of loose mulch where I suspect you're finding kitty poo. Cats like to scratch in loose soil, sand, or mulch. They're not likely to poop on top of a plant.

you can do anything from spreading a layer of compost/manure over the beds (called 'top dressing') to lifting your perennials, and rototilling (or forking, if you're in to the old-school, back-breaking ways) the same 'organic matter' into the bed, then resetting the plants, watering, and mulching the whole shebang. in most cases, it depends on the quality of the soil you started with, and whether the perennials you have are brats (things like roses and other heavy feeders) or not.

I like the plan very much, looooong clear view front to back from bath through the walk in closet, and a nice long view from the bedroom straight out through the WC area without staring at a toilet. Make sure the landscape architect/designer knows about those vista points from inside to carry through. I also love the idea of an exterior door directly to the garden/courtyard, I wouldn’t worry about that door conflicting with a vanity drawer/door next to it, the exterior door likely won’t be open much IMHO.