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How to lower TDS? (Mixing tap+RO?)

1049 Views 7 Replies 4 Participants Last post by  Griznatch
I'm having some initial algae issues in my newly scaped high tech. I would also like to try some crystal red shrimp in there. However I found that my tap is just outside the range for caridina shrimp. I found a zerowater faucet filter for $32. I basically creates RO water (0tds, 0kh/gh). Now I have to top off my tank (it's only 5 gallons) daily due to evaporation and because of this my TDS is around 300ppm in my tank. Out of the tap it is 192. My kh is 3-4 and gh 7-8.

If I buy the zerowater faucet filter, it claims to be good for up to 400 gal. Seeing as my tap doesn't have 500ppm of TDS, the filter should last about that long. If I use it strictly for my 5gal, that would give me enough water for almost a year with a weekly 50% water change and a gallon a week for top off.

If I buy the unit, how should I go about mixing the tap and RO to get my TDS in the desired range (120ppm)? I'm a bit confused on how this works. If I use 50/50 RO/tap, wouldn't my TDS still be 192? Or would it cut the TDS in half to 80? I understand that if I top off with strictly RO but use full tap for water changes, my TDS will just stay the same as it does out of the tap. How would using 50/50 for water changes affect my kh and gh? Would it then make me kh 1-2 and gh 3-4?

Thanks for clearing up my confusion! I'm still new to the idea of TDS as I've never really had to consider it before.

Would lower TDS have any affect on algae growth?
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