I would experiment with cutting your tap water (pure source, not treated or softened) with RO. Ideally it will be a simple dilution.
if you decide on the sun sun I'd recommend a mod to the pick or intake side.. they use cheap sectioned fittings that can draw air and the filter stops
is your water going thru a water softener treatment?
if so you may want to bypass the softener and use RO to mix water..
simply has a lot of reliable sources..
I got some small from Kenny Cheung and they turned out to be superior quality.
Once the nerites have gotten used to the tank, you'll see far fewer eggs. Mine dont even really lay eggs anymore. If I move them to a different tank though,