New To Freshwater

[gregzz4]

I ran FW for years, and I am not going to say I know it all, but it's not much different than a SW tank as far as testing goes.

I killed my first Goldfish when I was 7, and 38 years later, I think I have a handle on FW fishkeeping.

Using RO is a waste of money, but not time, when running FW tanks. If your system is plant deficient, you may want to use RO water, but do not run DI water, ever.
No matter how much algae you have in your system, no amount of clarified water is going to solve your problem.
You can run a UV sterilizer, but it won't fix a problem. It should only be used as a preventative measure.

An over-populated system is going to need 50% water changes every week. Ya, I know it. I've done it.
1-2" of fish/G of water is a heavily stocked FW tank !!!

Having many fast and slow growing plants will take care of most algae problems, if you do not over-feed. If you have no plants, you're on your own.

And when it comes down to it, Nitrates and Phosphates were my biggest enemies in my FW tanks.
Keep the PO4 and NO3 down to minimize algae issues and you're good to go

There's so much more to learn, but there's a start for ya
Good luck