You will have to weigh the skippy down to keep it from floating.
What ever you weigh it down with will take up filter space.

I have a 15,000 gallon pond. It is on a slope so we have a 40 inch retaining wall across the back.

We built a concrete platform while building the retaining wall for our bio falls and veggie filter.

My veggie filter is a 300 gallon stock tank.

For a pond your size, 2 -150 skippys will not add much in the way of filtration. I would go much larger.

Below is a pic with the veggie filter on the left.
{{gwi:215486}}

There is no reason you could not put your skippy filters in the pond instead of outside the pond. But......you DO need to clean them. I really don't care what nonsense the people at skippy try to feed people. Clear water is not necessarly good water. If you have never seen the inside of a skippy filter after just one year of service, you will not fully understand just how nasty and disgusting they are with all of that decaying fish poop in them. I do not know why they tell people that fish poop turns into sand. It is just riduclous to tell people that and also very irresponsible.

Ponds contain good bacteria and bad bacteria. The whole idea is to get a good healthy population of the good bacteria (the kind that converts your ammonia and nitrites into harmless nitrates) to be a strong population and to reduce the places where the harmful bacteria thrives. Bad bacteria thrives in places where there is no oxygen, such as in the sludge in the bottom of a filter or in the rotting sludge in the bottom of the pond. This bacteria is the kind that causes ulcers and rotting fins on fish. As the sludge builds up in the filter, there is less and less area where waterflow brings oxygen into the filter media and the good bacteria needs that oxygenated water to thrive. When a filter is cleaned, the sludge is all rinsed out of the bottom. This is not harming the good bacteria at all, since the good bacteria is not living in that sludge anyway....it is living on the bio-media. Bio-media can be rinsed with pond water or non-chlorinated water also without harming it. You do not have to start over after cleaning the filter and you never need to add any enzymes or bottled bacteria to get a pond and filter established.

I have used skippy filters on small water gardens in the past and still use them on my quarantine tanks, but two 150 gallon skippy is simply not enough filtration if you intend to keep koi. You will need a bare minimum of two 300 gallon skippy filters.

You need to have pumps large enough to turn over all of the water in your pond at least once every 1.5 hours. So if your pond is 13,000 gallons you will need two pumps that each move nearly 5000 gallons per hour.

If you want to put the filters inside the pond, the biggest problem you will encounter is when you drain them for cleaning. Running the plumbing is easy enough....just install a bulk head fitting in the pool wall and run the drain line through the bulkhead. Keep the valve inside the pond, under water so it does not freeze in the winter. But when you empty the filter, it will float. I am not sure how to tell you to overcome this problem. It will need to be weighted down with something pretty darn heavy to keep it down.

Since your pool is raised, have you though about using 55 gallon barrels for filtration instead of stock tanks? They are taller and very cheap, and you can build some wonderful DIY filters that work much, much better than a skippy filter works. You can actually put some bottom drain lines in the pool and gravity flow to the filters, then pump the water back to the pond. That way, the top of the filters would not even stick up above the top of the pool.

Here is a link that might be useful: lots of DIY filteration stuff

I agree with ccoombs. She has given you great advice.

I have my barrel filters and external pumps behind the wall and it works really well.

The filters are weighted with cinder block.

I keep them weighted down in case my GFCI outlet trips and my pump shuts off. If my check valves fail, the filter box will drain empty into the pond and it will float and make a mess. Also, if you do drain it to clean it, the cinder blocks keep it from floating.

I have a drain in the stock tanks for when I drain the filter to cut back overgrown plants.

HTH

wow 1sst. ur pond looks amazing, please post more pictures, where are you located?

lsst- your pond is better than Disneyland. What a lovely thing you have created.

Pondluvr, I can't believe you posted this question just as I was about to email Skippy the same question. I have a similar situation, and wondered how well an in-pond biological filter would work. Thanks for posting it.
Renee