I would try dripping kalkwasser, especially in a 225. One of the best long-term solutions you can get is to make or buy a calcium reactor setup--it'll be about $400 when finished but you won't ever have that problem again.
Experiment with the amount of dissolved kalkwasser in your topoff water, drip slowly and test for pH rises that are out of the ordinary. One of the best ways to dose kalk is to buy a $30 Kent aquadoser and mix the water/kalk in there and slowly drip it constantly into your sump. About one drop every three seconds is a decent rate--kalk density should be determined using max pH and alkalinity values to prevent tank stress, kalk has a very high pH roughly around 12 IIRC.
A critical time of day in your kalkwasser evaluation is right before lights off. pH values are highest at this point due to photosynthetic reactions in the tank, and should top out at 8.4 ideally in my opinion. Conversely, the lights off ciritical period is at dawn just before lights on, when the cumulative waste gasses of respiration can lower pH by a small degree. Some time their kalkwasser to only come on at night, working against this shift. For the most part however, a continual drip suffices and still keeps the pH fairly stable--I've seen a rather simple kalk dripper run a 180 SPS tank just fine.
