I'll stay out of the bottom drain designs but there will likely be plenty of others who can and will post.
The damage done by koi to plants usually occurs as they dig in the pots which dislodges the roots. If you put the plants in a deep enough pot, the pebbles will fall back and the plant will stay potted. You could also cover the pot with wire such as chicken wire fencing which would keep the koi out. I regularly buy duckweed and feed them shelled peas or melon which seems to curtail their appetite.
Rocks on the bottom is a subject that will invite endless arguments on this forum, LOL! IMHO, if you have the time and energy to chase after sewage, go for it! It is not a pretty job.
I am of the opinion that the best time to purchase pond equipment is just before they put it into storage until spring. As I said to one merchant as I made an offer substantially under his retail, he could sell it to me now and at least make back his investment or spend the money for keeping the stuff in storage. I have had only one person say no but he called me a week later and offered me the equipment to me at his cost. Sometimes it pays to be pushy (and married to an accountant). Sandy

Congratulations on taking the next step! OK....where do I start.

First, consider going bigger. A LOT bigger. Koi get very large, over 30" in length and need space. Koi should have between 300 and 500 gallons each, so at your planned 1600 gallons you could realistically expect to keep no more than 5 koi. If you can double that to 3000 gallons you would be much better off. Depth needs to be a minimum of 36", although 48" is much better. 36" isn't very deep for a 32" long fish.

Bottom drains are a MUST. Koi are very messy animals and produce a lot of waste. Most of that waste will sink right to the bottom and sit there until you remove it by vacumming, or the bottom drain carries it to the filter. You can buy bottom drains, commercially made. All you do is set the base in a bed of concrete in the bottom of the pond and attach the pipe that will be burried under the pond and come up at the side of the pond where it ties into the filter. Lay the liner in and get it secured. Then cut a hole in the liner in the center of the drain. Use sealant to prevent leakes and attach the plastic ring that comes with it with the stainless screws they provide you with. I have installed 5 drains in my own ponds and never had a leak. Get a 4" drain...anything smaller just won't move enough water.

small koi will coexist peacefully with plants.....but the bigger the koi get, the more they will damage the plants. Koi love to dig in the pots and shread leaves. That is just their nature. You can have plants that stick up out of the water (iris, cattails, etc), just use a heave pot and use heavy round river rocks all on top of the soil to keep the koi out. And you many find that as your koi mature, even the rocks won't keep them out.

Rocks on the bottom are a HUGE mistake. They trap debris that should not be left in the pond to decay. they provide a safe harbor for bacteria and parasites to breed, and koi can become injured on them. Seriously....leave them out. They do not look natural to me at all. In nature, you do see creeks with rocky bottoms, but I have never seen a lake or pond with a rock bottom. I love the look of a black liner bottom. When you have a beautiful collection of colorful koi swimming against that black bottom, you see the true beauty of the fish without the distraction of the rocks. Besides....the rocks will get covered in algae and won't look as nice as you think. I prefer to see koi when I gaze into a pond and not green rocks.

A good supplier of equipment is AZ ponds. You can find them on the web. They are a little short on customer service, but their prices are unbeatable.

Oh yeah....you need a skimmer too.

You may want to check out a website called koishack. There are many wonderful threads over there in the construction forum with loads and loads of pictures. I just completed a new filter for one of my ponds that works every bit as well as a $1500 nexus filtes and it cost me around $150 to make it. Instructions for that are over there also.

There are a lot of wonderful koi clubs in Texas. You might want to get in touch with some of them and get some guidance locally too.

Attached is a link for the AKCA, Associated Koi Clubs of America. They have a wonderful web site that may be of interest to you as well. www.akca.org

Here is a link that might be useful: AKCA Koi Club list

1) I have a successful koi pond without a bottom drain. However, if there is no bottom drain, you must have an alternate method of cleaning. The BD is easier, but not a must. I use a Pond Vac. If you have a heavy fish load, then a BD would definitely be beneficial.

2) Koi do pull up plants, but that can be eliminated by covering the top of soil or sand inside the pots with rocks. Some people use lava rocks because they are sharper and koi don't like poking their noses around in it. I have lilies, pickerel, cattails and bacopa in my pond, and all are doing well. Now, the water hyacinth is another story . . .

3) I have a thin layer of small rocks, 1 to 2 inches in diameter, in the bottom of my pond just barely covering the liner, and I love the way they look. I use my pond vac to get under the rocks by pushing them around with the nozzle. My pond bottom is kept clean with routine vacuuming. If you don't use a vac then over time, yes you will get fish poop and other debris around them that can cause problems.

4) There are many good pond systems on the internet. YOu might also find some locally at hardscape stores or pond specialty stores. I have a Pond Eco-System , and love it! I bought mine locally, but they are available at the following link.

There are strong, almost rabid feelings on both sides of the issue when talking about certain aspects of ponding, i.e. bottom drains, rocks, etc, but its really what you prefer. Bottom drains are great, but most of the ornamental koi ponds in my area do not have one and are doing just fine. I was squeemish about putting a hole in my liner, but I'm told that if they're done properly they will not leak.

Here is a link that might be useful: Itsparadiseathome

There are also retrofitted or suction type bottom drains, if you are interested in those. I've never used one and therefore don't know how good they are, but I have considered them as an option. You have a lot of choices. Try Google searching various products and equipment to find what works best for your needs.

Thanks for the good ideas, everyone- I have a long road ahead, but the ride should be awesome...

bwalters,

If you go with a bottom drain, it is a good idea to slope bottom towards drain so as to allow the crud to collect and be removed there at the BD.

My koi do not bother my potted plants because I placed red bricks (whole and parts) around stalks. They can not get to rooting in the soil (though it makes for a heavy container when moving).

I'm in agreement with ccoombs1. Go as big as you can (I maxed out, because I knew I'd be regretting too soon after completion). Koi get big... fast. Also the larger the body of water, the more of a cushion you have in regards to balance of the water chemistry (aka green water/ or stressed fish).

LP

The only plant my koi bother is a baby lilly I have they love to nose it out of the pot and push it around.. I have lillies, sensitive plants, iris, hosta, parrot feather and water lettuce in my pond. I agree with the other poster go bigger, we wished we would have gone bigger the second we finished. we have a beach area that is approx.3-6 inches deep and we river rocked it but left the deepest part without rocks and with the plants and fish poo you cant tell we dont have any there. Darla

I have seen several responses suggesting that I go bigger; believe me, I'd build a 10,000 gallon pond if there were no other considerations! Among my limitations are space, leaving some room for the kids to play, and the wife's not wanting to have a large pond (and not necessarily in that order!).

I have a good sense of the room that each fish needs, so I am thinking of no more than 5 or 6 koi at the most.

(Maybe if I behave really well, I'll be able to negotiate a 2,000 gallon pond out of her!)