The internet can be a source of some very good information and some great misinformation.  I found many of these sites below by using the google search engine and entering phrases like "koi pond aeration" in the search field.  Here are some sites that I like.  Again, the information presented is only as good as the builder of the site.

Other resources, such as books, stores, and internet venders are some of the ones I am familiar with.  I am sure that 'most' stores and internet venders are well-intentioned and honest, but I will only list the ones I am familiar with.  Many other vendors who use the web can be found in their ads listed in KOI-USA magazine.  

Books and periodicals

The best general book on koi and koi culture that I have found is 'Koi Kichi' by Peter Waddington. My one criticism of this book is that it is expensive.  The word 'kichi' is Japanese for 'crazy.'  Waddington owns an English koi store called Infiltration.    He has several practical ideas on filtering, and he is now pushing what he believes to be the ultimate filter.  He is also an importer of koi and supplies to the UK.  He has been interviewed extensively, so just go to goggle, and then type in 'Waddington koi' to get lots of links.

If the $125.00 price tag of "Koi Kichi" is a bit high for your budget, then "The Tetra Encyclopedia of Koi" published by Tetra Press is a fair substitute.  Its section on koi types is good, the pictures are nice, but if you are building a pond larger than 1000 gallons, buy Waddington's book and study his designs on filters before proceeding. The paperback version is more affordable the the hardcover and it is now available. 

Dr. Eric Johnson, a Veterinarian and fish health special is, has written a book titled "Koi Health and Disease."  The book is available at most koi stores as well as over his web site koivet.com   The koivet site has lots of information but you need the buy the book.  Be sure to sign up for his listserv on the site.  Dr Johnson is being given stuff to try out and review.  He never accepts cash for his evaluations, so his reports are a source of unbiased information.  If you need injectibles, I have found that taking a copy of his book to your local vet helps.  Your local vet will look at you like you are 'kichi,' but if you show him the page in Doc Johnson's book describing symptoms and treatment, you usually get the supplies you need.  Doc Johnson's book also has a lot of information on water quality.  

KOI-USA is the magazine for all American koi lovers.  The ideas, ads, and pictures make it a must have.  You can use the website to subscribe, change your address, and check on the contents on the website.  There are also a bunch of links.

Vendors I have used and Southern California Koi Dealers 

I have done business with all of the following companies and been fairly treated by each.  A word of warning here.  Some venders will push various product lines.  Many products are comparable but dealers often don't stock products available at a discount over the internet.  This is particularly true of filters.   Remember when you buy something from a reputable dealer, you are also 'paying' for their expertise!

Aqua Art is a vendor that stocks typical stuff but also includes Art and statuary.

Eastern Nishikigoi has fish, medicine, supplies

Laguna Koi has supplies and information at their site.  Another good excuse to visit Laguna Koi is to visit the city and beaches of Laguna.  It is a beautiful location.

Koiko Toni, the owner, actually came to my house to show me how to give shots to some fish I had suffering from ulcer disease.  The owner's wife is a landscape architect.  People living in Temecula and Murrieta should check them out.

Koistuff is one of the sites sponsoring the koivet site.  Often the items mentioned in koivet are easiest to get here and at Koicamp.  Both have staple and high quality medicated food.  

Mystic Koi is a hop-skip-and-a-jump from my house.  The store has a large complete lie of supplies and they import high quality koi from Taiwan and Japan.  Their web site has some useful product information, but Sandy, Shawn, and the staff are very helpful in person, so a visit Upland is recommended if you live in the vicinity.  They have one of the largest selling area in Southern California.  What makes their facility unique are the demonstration ponds.  The demonstration area consists of half a dozen different ponds in various sizes and styles, all fully landscaped.    

Oxymax is the place to go for high performance aeration devices.  Jeff has an interesting view about pond filtration.  He believes that with maximum water oxygen saturation and good circulation, most biological filtration is done by the oxygen eating bacteria lodged on the pond's walls and bottom and water clarity will result no matter what filter system you have.  My 'meg2' venturi aerator is a champ.

Tse koi sells products and imports koi.

W Lim mainly designs, manufactures, and distributes major pond components including pumps and a 1500 gallon molded pond that looks ideal for someone who wants a 'small' pond designed to optimize viewing and health.  Lim's products are available widely.  I think his pumps are top notch. His data on pump performance is first rate.  If you ever attend a koi seminar where he is showing his products, take the time to talk to him.  It is time well spent.

Information Sites

Many commercial sites devote space to information.  A bit of warning though, different people have different views.  If a company represents one product line, they aren't going to be objective about competitive products that they do not represent.

The Associated Koi Clubs of America has a lot of information and services including a bookstore, lists of dealers and clubs and pond pictures.

For koi disease, see koivet.  For a symptom list all in one click the 'fish symptoms' page.  Finally there is the Fishdoc, who is the United Kingdom's alternative to the koivet.

Several commercial sites have lots of information content, including the pond link or subject selector of pond net, the koi.net has a whole 'beginner's guide' to koi,  the Pond Authority's page, the mykoi page

Other internet sites have good descriptions and pictures of various koi classifications, including Pan Intercorp,  

There are also pages of links such Koi Links page

Other Pond Sites

The pond pictures of the Associated Koi Clubs has a 'pond page' with plenty of pictures and specifications of ponds.  Go to the AKCA site and click ponds.

Internet Sources of Koi

Richard Tsai is a student from Taiwan studying in Southern California.  His father is a well-known koi expert and President of Taiwan's Koi Society as well as a internationally known koi judge, breeder, and raiser of jumbo koi.  I have gotten koi from the Tsai's and I was very satisfied.  I have also had the pleasure of hosting the Tsai's at my home where koi culture was discussed.  Richard's father, Dr. Tsai, suggested modifications to my filter system that improved its performance and reduced its maintenance.  The site contains several thought provoking articles are koi and water quality.   Richard's koi site  now takes second priority to his studies but the pictures of the koi breed and raised by the Tsai's as well as pictures of the Tsai's pond in Taipei make the site worth visiting.

In the deserts of California is Koi Heaven, whose site is intriguing but I have not yet taken a drive to visit them.

Koi Breeder Sites

I have come to the opinion that breeding and bloodlines are very important when selecting koi.  If a dealer says the fish is from Sakai's farm, what does that mean?  Many breeders specialize.  I am trying to get a list of breeders and their specialties as well as their success in raising and showing koi.  What I am looking for are breeders who breed for jumbo size, good confirmation, disease resistance, and koi that stay true to type.  I am tired of buying a kohaku (a red and white koi) that turns into a white fish two years later

Koi Club Links

Several Southern California Koi Clubs have asked me to put links to them.  Because of this web site I have actually spoken to several.

The Nishiki Koi Club meets in Orange County  Their website is  http://www.nishikikoiclub.com/

The Inland Koi Society meets in and around Riverside,website is http://www.inlandkoisociety.org/

Other Koi Related Links

One of the games websites play to 'increase' their rankings which improves where various search engines place the site is to cross-reference with related sites.  I do not endorse the sites listed below, but I too would like to increase my rankings.  Please let me know if any of the sites do things like pop-ups and I will remove the link.

Link Text: Gardening
Description: An online resource for lovers of gardening. Url: http://www.mygarden.net.au

Here is a site that describes itself as THE resource for keeping nishkigoi is           http://www.nishikigoi-info.com/

  Top 100 Gardening is more Garden than Koi.  Clicking on the banner opens a new page to their site on your browser