As the water starts to warm up during the spring months so do the parasites and algae.
Algae can be controlled by adding Algaefix as a chemical additive or by turning on the UV Sterilizer. String algae will grow well in cool water that gets a lot of sunlight so you may need to attack it with a scrub brush or net. Your fish will tend to begin eating the string algae too, which may dislodge more of it than is eaten. Keep an eye on that pump leaf basket daily, or dump your settlement chamber more frequently to keep the algae from migrating to the rest of you filtration.
Parasites have different life cycles at different water temperature. There is not a lot of data about each parasite’s ideal temperatures and some treatments may not work at low temperatures. Potassium Permanganate is an effective treatment to use in cold water and higher temperatures and it kills a broad spectrum of parasites. Use additional aeration if water temperature is above 65*f/18c. Other treatments may require multiple applications to prevent a new outbreak from eggs. Identifying which parasites you have is also key to finding the best treatment for this time of year. Learn to scrape and scope or hire a local professional. ICK and flukes may not be affected by PP.
Water changes can be an excellent alternative this time of year. It will remove stagnant water from the winter, reduce free floating algae, reduce discoloration from debris, and reduce some of the parasite population. Be sure to de-chlorinate any new water for maximum fish health. Monitor your pH as well since large water changes will cause a fluctuation. I prefer to do large water changes over 3-4 days rather than 50%+ in one day. It is less effective but also less stress for the fish.
Do keep in mind that your fish’s immune system is not yet fully functional and nor is his digestive system. Don’t be tempted to over feed which can lead to other diseases and problems. Too much food in water also encourages algae growth.