Soft water

[Bryon]

Hello everyone,
I had always used straight tap water for my changes and all has been well except for a constantly blooming diatom.
In spite of this, most recommendations were to use ro.
So I bought an ro unit (from airwaterice).
My tap water is,.062 ppm. Run it through the ro and it drops to .001.
So now I have to raise it back up to bring it into an effective range, (100 to 300 ppm is the recommendation from various boards) so I use Kent's RO Right.
At Kent's recommended rate of product, (1/2 tsp. per 10 gal.s) the tds only rises to .092 ppm.
I can continue to raise the tds, but my ? is this.
Am I just replacing the ro water with water that has solids in it, making the ro water pointless, or am I ridding the tap water of "bad" solids and raplacing them with "good" solids? If so fine, but if not then why the expense (4 gal.s down the drain for every gal. of pure product) to get back to the starting point?
I realize a diatom is generally harmless and that I can limit it somewhat with Hipostamus (?) plecos, but then why the ro?
All responses are welcome.

Bryon

[ILLUSN]

i wouldn't bother, just give them a good wipe down, bristlenoses will eat diatoms, or increase your light and they should go away.