I have an I can do it attitude so 18 years ago my 14 year old daughter and I dug a pond, put some old carpet down, a 20 year liner etc.. and found a book that told us a tote some lava rock and a pond pump is all we needed. This worked quite well for 17 years . The liner failed last year , the Koi we got 15 years ago at 3" now 18-20" , 11 of them had to be moved to the pond we were making as our second pond not seasoned yet and a bit smaller. first pond was 14 x16 3ft deep with a 2x2 x2 upper pond with a stream to the main pond. new pond is 14 x14 waterfall not done. we lost 5 0f our big koi since moving them first due to injury as it was within a week . The others gradually over 6 months, the largest measured 26" 14# I'm sick about it but I assume I just had beginners luck with the other pond we never had any issues we even had baby koi and turtles. I have bought a 40 year liner and a new pump and filter to the tune of about $1,000 to revamp the old pond which is currently empty. the 5 koi I have left seem OK they are in the pond with the lava rock filter and 4 large aerating rocks with a lot of floating plants. I have 2 wild frogs that seem to like the pond and the plants have tiny worms. Would love to hear any thoughts or suggestions!