I like the Koi.
As for the horses, do you want my honest advice? I shall assume you do.
YOu are really close to haveing enough accuracy to make the horse feel real, that it occupies space and has weight and is sitting or pushing off the ground.
However, sometimes it looks a bit like you are "fudging" it. I mean, you need to really spend some time looking in detail at how the horse is put together; the legs for example. YOur horse's rear legs kind of have a hock, then there are some bumps down below it, so I am not sure what those are? Really look at the front leg and how straight it is exept the knee. Look at how the weighted shoulder will be higher than the non weighted, and same goes for the hip.
The muscleing of the chest area of the first picture is really good but then the front leg (left) is a bit wonky.
the Gypsy vanner has a pretty good action feel to it, just minor things in the rear legs that just dont read quite right.
Lastly, and I feel like I am being awfully harsh, horse's heads are pretty large. Yours seem a bit too small for their bodies. Check your porportions.
Did I go overboard? Dont' feel bad. I assume that people want details. So I oblige. HOpe I have not hurt your feelings.
There is potential, that's why I take the time to resond at length.