15 gallon tank which is about 4-5 months old has broken out with a green/white cloudy water. I recently did a 40% water change and cleaned out the filter. Any ideas what could be up? Fairly new to aquarium keeping.
Is the tank in direct sunlight? What is the lighting period on the aquarium? What are your water paremeters? (pH, Ammonia, Nitrite, Nitrates) how did you clean the filter and what is the stock in your aquarium?
The more information you could provide us the better.
Since you rinsed your filter with tap water you probably lost some bb, you might be having a bacterial bloom. Or an algae bloom, 13 hours is quite a long time to have your tank lights on, most people aim for around 8 hours. Try leaving the lights off for a day and see if it improves any.