Spring means it's time to open your pond. Hopefully you've kept most of the leaves out of the pond and removed a lot of the gunk on the bottom of your pond last fall. If not, those are two tasks to start with. A water change of 50% is helpful and not overly stressing to your fish. If you have KOI you need to add a dechlorinator for the amount of water being replaced.
Next, it's time to put your pump back into the pond. Give your filter/biofilter a cleaning and add new filter media of whatever type your filter uses. Folks who are using our lava rocks just place back in the filters. Once your filter and pump are hooked up and running, you can seed your pond with nitrifying bacteria. Microbe-Lift P/L, Pond Perfect, Ultra Clear, The Best in our opinion is "Healthy Koi" has a cold water bacteria in it and will work is water as below 55*. These Bacteria will quickly establish a good colony of beneficial bacteria within your pond and filter. Make sure the water temperature is 55* or warmer if not using "Healthy Koi", if not the bacteria will probably die as you put.
Healthy Koi reduces ammonia and nitrogen levels, reduces noxious odors, improves dissolved oxygen, breaks down algae and reduces buildup of bird droppings. It is 100% safe to humans, animals and plant life. It is non-toxic. Healthy Koi converts nitrites to nitrate, lowering ammonia levels.
Spring is also the time to re-pot any marginal plants and water lilies that have outgrown their containers. When repotting marginals at this time of year, don't add fertilizer. Let the marginal plants use the nutrients in the pond that are feeding the algae growth this time of year. Make sure to trim off any old foliage from last year if you haven't done so already. If you over wintered your plants at the deepest part of your pond, you can now put them back to their proper places. With water lilies it helps them to grow faster if they are closer to the ponds surface. Once they start growing, lower them gradually over several weeks to their proper depth in the pond.
Don't add tropical plants until after the last frost date for your area, in Garden City, that is usually mid-May .
As your fish start to become active they'll graze on the algae in the pond. This algae is a good first meal for your fish. Do not begin feeding fish food until the water temperature has stabilized at 55 Degrees. Feeding at too low a temperature can be harmful to your fish.
Spring is a good time to check your water quality and make any necessary adjustments. Do not add salt before doing a test for salinity.
No matter what anybody says, green water is caused by one thing and one thing only. ORGANICS. Organics are the main source of nutrients in the ponds or water gardens. The nutrients are what feeds the algae, the algae is a plant and it's green, green water. Organics can get in the water gardens usually 4 different ways.
1st - Potting your plants is a soil based mix. We use an aquatic mix, it's a fired clay that has been treated like a ceramic pot. It's basically like a clay pot. No nutrients in it now. No Green water.
2nd - by run off of fertilizer that was either put on in the fall of last year your fall feeding, this years spring feed or over sprayed by the lawn services. Make sure that your run off doesn't make it to the pond or water garden divert it, Make sure that the lawn sprayer doesn't have drift on a windy day. No Green water.
3rd - to many fish for the eco system to handle. Either the system is to young or over crowded by putting to many fish in at one time. You should not be putting fish in the pond until their is no more green water. Then only 2 fish at a time 2 weeks apart. The pond has to grow into the fish not the fish into the pond. Also we recommend only 1" of fish for every 10 gallons of water. Example is 1000 gal. pond 100 inches of fish. That's 10 10" fish, 20 5" fish and remember that all those little 1" fish all count. If you follow 1 and 2 and get to 3. No Green water.
4th - is and probably the most common is feeding to much. Fish do not need to feed everyday. At 50* a 5" fish will take about 5 days to digest ONE pellet of food.
One thing that has worked very well for us and many others is a very simple and GREEN solution.
All you have to do is get a good sump pump ( we have one 1200gph with a life time warranty $149.99) attach it to your garden hose and water your garden and flower beds with the pond water. Then refill the pond.
My pond is so clear I have to add dye to it so the fish do not get sun burned.