Welcome to the forum from Plymouth in the UK
Steve I like that "welcome to the never ending hobby", sounds like us that your an old timer at fish keeping, weve been koi keeping for 27 years now.
How are you on koi health issues my friend we can always use some more knowledge on the health forum ?
Dave
Hi Dave/Val
I work a lot with environmental issues and water certainly is one of them. Kinda nice that my old hobbies always seem to fit in.
First thing is to know your water. I was lucky to have access to an atomic absorption machine while I was doing research about thirty years ago. I ran over 200 tests on my springs in my spare time. Hardness, minerals, particulate matter, nitrates ect help in chasing problems, but usually its bacteria, parasites or oxygen depletion from overcrowding Can't really blame people for wanting to see a mass of fish

swimming in schools. In the years I've lost my share.

If I see a fish in distress He/She goes into isolation and possibly medication. I use this 500 gal partition filter(see pics) for this and a lot of other jobs that involve water.
NO, I did not shell out$4500 for this sweet solution, but my engineer buddy bought it as a deal and found it too big to filter his pond. I don't think he gave it a lot of thought for its other uses and his wife considered it an eyesore. He and I trade water lilies etc.
I like your credo.Fish are for life; so is my 38 year old Parrot

(still have all my fingers.); and don't forget my Greyhound hobby.
Keep busy and you never get old. Thanks for the heads up on the Health forum. I always remember advice is cheep and you can lead a horse to Water, but he won't always drink.
PS I'm British decent, as was my wife. I just finished entertaining the second bunch of relatives from Merry Old, this year.
Steve