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?