Calcium reactor too big?

[RuGlu6]

No, as long as you have calcium consuming corals clams etc. you are ok.

Just keep Ph effluent at say 6.9 (slightly below Ph7.0.) usual recommended Ph effluent from properly sized reactor should be at 6.5 if your over sized keep it higher at 6.9 and you will be OK.
remember to check calcium and kh regularly in first few month so you know where you are at.
Then if you need more calcium lower ph slightly (more Co2 bubbles) and test in 24-48 hrs. this will increase Kh as well.
If you have too much calcium then increase effluent drip flow from reactor.
Good starting point is steady drip at 1-2 drops per second and Ph effluent at 6.9 and go from there as per above.
hth.