Well, the visit to the vet with my cat cost a lot less than expected, so if a diatom or UV system is not too expensive, I can probably afford to get one.
Where is a good place to get one and do I have to run it all the time now or just until the green water clears up?
Edit: What wattage UVS would I need? Is a 9watt Jebo good enough? It's the cheapest system I can find, running at $35.