I use cole parmer peristaltic pumps. You can find used ones for cheap I got mine from vancouver coastal health they used them as artificial hearts. Because I dose kalk in my top up water my ATO pumps would only last about 6 months to 1 year. The pumps come up as goverment surplus too check this site
https://www.gcsurplus.ca/mn-eng.cfm?snc=wfsav