drop in cal and alk

[will8]

hiya all,
i have been having a on going problem keeping ALK above 7dkh, i do a 10%pwc every week with D+D H2Ocean pro+. its rises to 9dkh when though out the week it drops down to 7. i top up with RO/DI about 2/3 litres every other day and someone said adding aragamight to the top up water. but this is not helping much.
the calcuim starting to drop from 440ppm on PWC day to 420ppm the day before PWC day, it is PWC day today and it has dropped to 380ppm, i guess its because i have 7 LPS in the tank. i have ordered some Kent marine liquid calcuim to help with the calcuim. i did dose with kent dkh buffer but my tank is 100 gallon and its does not last long. what else can i do to keep the levels up,

cheers will

[Innovator]

I would use a ca/alk supplement, such as ESV or Kent, to attain the levels you want and kalkwasser to keep them there. Frequent water changes will always alter them so instead of dosing top-off water, dose the mixing vat (after 24hr mixing) instead because you perform water changes weekly. Make sure to test the mixing vat prior to use for each water change. Baking soda and Mrs. Wages pickling lime can be cheaper alternatives to brand-specific alk and kalkwasser.

[will8]

cheers, just read abit about dosing kalk and pickling lime, as i have never use it before, its says it should be dripped in to the tank at a rate of 1-2 drops.
are you saying dose my fresh salted water (aftering 24h mixing) with kalkwasser then test and then do a PWC as normal.

thanks

[Innovator]

You can dose the vat with kalkwasser or use a ca/alk supplement system. In using pickling lime, be aware that pH will spike rapidly as its pH is about 12. Either way you will have to experiment in order to get the correct dosing amount and test before your water changes. Whether you've seen it or not, here you go :http://home.comcast.net/~jdieck1/chem_calc3.html