how often should I dose b-ionic?

everyday. and dose by what it says. but be sure to remember if u have a 10 gallon tank, with LR and sand, you dont have 10 gallons anymore.
I dosed daily when I was using it. You'll need calcium and alkalinity test kits make sure the tank parameters are okay and then to get a baseline dosage.
Anyone know of a reasonably priced dosing pump for B-ionic? My apologies for jumping in on your thread bboy.
Test for it + dose depending on demand [which will change over the course of the tank's lifetime].

When I first started using it, I would dose every two or three days, maybe 15-20ml to my 58g. A few years later, I now dose 35ml daily to that same system ... due to change in demand, corals I keep.

In my opinion, dosing daily [or multiple times] smaller portions is a better idea than less frequent/more.

Honestly, I would test your tank [and test newly mixed saltwater, see what waterchanges are doing] for both Alkalinity and Calcium. I tend to watch Alkalinity more - as mine seems a little more variable - I `see' demand more in this IMO.

Perhaps start a minimal dosing regimen of 2-part, I'd `undershoot' at first. Test a few days to a week later - see where levels have gone. If they're remaining about where they started - then you're relatively close to demand. If they fell a bit ... then you'll want to increase dosing.

Keeping some sort of log/record/calendar with these test results is useful IMO. While I don't record `normal' readings anymore ... it's useful to see how demand/dosing is matching over time. [I should have recorded dosing amounts, too]

But I'd work out your demand through a few week to month period of regular testing + regimented dosing ... and check on that regularly thereafter.

In the almost 3 years my 58 has been running, demand has varied a lot. When I've slacked from testing, I've found that levels can get off within a month's time [even with regular waterchanges] ... just my experience. And it's not a linear-type increase in demand - there's been periods where IMO demand fell for a month or so ... and periods when everything thrived and demand skyrocketed.
i agree with MiddletonMark. you should never dose something by just using the recommend amount. always test your water for what youre dosing, then add what is needed. my tank is fairly stable with the Alk and Calc. i can dose 60ml of both parts (i use Randys homemade 2 Part) everyday and know at the end of the week the levels are going to be close to prefect (or atleast what i consider perfect :) ).