We didn't wash our gravel, just too much of it. The first summer had just a 125 gph pump running while working on the pond and bog i.e. building. The water was murky for the entire summer. The next spring we installed the 4200 gph pump, it pushed pea gravel dirt into the pond, didn't want to drain and start over, too much water and it was so dry. So I gave it time, it was slowly clearing. I read in here about jw, sissy and others using the quilt batting. I put some under the water fall, it did catch a lot of muck.
Being a patient person............lol......I then built a temporary fines skippy type filter, put the low flow pump on it, used a spare 55 gallon barrel we had. Within 3-4 days the water went crystal clear, it has stayed clear since. The temp skippy sits unused on lower deck. The only time we have non clear water is when I net the bottom, or muck with the lilies. The water even then will clear up in just a few hours.
I have not needed to net the bottom, this summer so far, except the spring start up for leaves, there is no muck collecting worth netting. The plants are using up whatever the fish are creating.
The fish, before plants started to grow, very nicely spawned in the lily tubs with their new kitty litter. I now have a layer of kitty litter on the bottom of the pond around the lilies so it stirs up when I walk in the pond to groom them. But clears quickly. They knocked enough out of each pot to make a small mess, but the lilies are fine.
Any water change will help the dirt is just very fine, needs to settle or be collected by the gravel. I don't purge my bog, we have drained it twice to work on piping no muck comes out.
This spring before start up the water was getting the glacier water look, slightly cloudy. Once we installed the pump it was clear 24 hours later.