Spring is a tricky time for koi keepers with many problems and koi illnesses to be averted so the following advice will help get the koi and pond up and ready for this season.
Now is the time to clean the filters, if you haven't done it over winter. Use pond water to do this or if you are sure your filters are bomb proof then use a hose. Remember filters arent fully mature for over 4 years.
10% water changes should have been done weekly over winter but if not start now, using dechlorinator of course.
Time also to think about buying a new UV as they only stay efficient for about 1 year and no one wants an algeal bloom and green water.
You may also have noticed that the blanket weed is raising its ugly head again with the sunshine so keep an eye on it and scoop it out remembering to leave it on the side of the pond for a while for the pond life to crawl back into the pond.
On warm sunny days koi will start to become active and get nearer to the water surface and may take a little food. Try throwing in 5 or 6 pellets of low protein food and see if they get eaten within 10 mins, if not scoop them out and don't feed again for a few days. Then try again.
When feeding the koi really take a good look at the koi as this is the time and the next few weeks when the koi immune system isnt running so well but the pond bacteria are and so koi get sick very quickly. A problem spotted early is a problem that can be solved/cured.
As you have started to feed again, little by little, then your water parameters may go slightly haywire as the filter bacteria need to catch up so make sure you have your water testing kits and test every few days until you KNOW they are stable.
Remember koi haven't been fed since last year (October, November probably) so we have to gently reintroduce food so as not to shock their systems.
Just a reminder here that koi do not have stomachs they only have intestines so food fed too early and in too biggfer quatities stays in the intestines and rots on a cold day (Koi are polykathermic) eventually producing bacterial gas that explodes the intestines and kills the koi.
Frogs are appearing about now so scoop them out of your koi pond and place them somewhere more suitable as they carry major bacteria that can harm koi plus they tend to latch onto koi if no suitable female frog is around and have been known to kill koi by clamping their gills shut.
This advice also apply to goldfish and other pond fish.
Hope this helps
Jackie