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reverse osmosis


New Member
hi, i have hard water and was using a free ro source until recently. what type of filtering systems do you use? i have 2 15 gallon aquariums and limited space, any recommendations for something small? i would also be looking for a conductivity/ ph/ temp/ tds meter(not necessarily all in one). i used a expensive meter that also took other measurements a while ago but im looking for something cheaper now and the little hand held ones i was looking at dont seem very good. any recomendations?

Mike Wise

Staff member
5 Year Member
There are many very good R/O units sold. Do a search here on the forum for past discussions. I do have 1 recommendation, however. When you buy the unit, buy a reverse flush accessory, too. In areas with hard water it will extend the life of the membrane.


Well-Known Member
5 Year Member
For pH, the cheap meters are not very good, and the good ones require maintenance that I find hard to keep up with. So I rely on color dye test kits for pH. However, conductivity meters are much simpler than a pH meter, and even the cheap ones are pretty good and long-lasting. TDS and salinity meters are really just conductivity meters with built-in conversion factors. You can convert conductivity to "TDS" yourself:

Conductivity (microSiemens) x 0.50 = approximate TDS (mg/L) if NaCl is the predominant dissolved substance (mono-valent ions).
Conductivity (microSiemens) x 0.65 = approximate TDS for most natural fresh water with a typical mix of mono- and di-valent ions.

Megan Fischer

New Member
I also use colour indicator tests for ph.
I use an fairly inexpensive hand held tds meter that also displays temp.
HM aquapro TDS pen