Lance's 225 gal tank

[Lance]

Precipitate. How come? Help!

Lately I've been getting a lot of precipitate build-up in the return pump, (Mag 7). The PH's in the DT have no build-up at all. I just tested and the params are: Ca: 410; Alk: 7; Mg: 1290; pH: 8.0 These numbers stay quite constant from week to week. I use the two-part from BRS and dose via 2x Drew's Dosers. Both dosers drip into the return section of the sump; calcium in the morning and alkalinity in the evening. Is it possible that there is not enough water movement in the sump? I estimate flow through the sump at about 280 GPH. Any ideas?

P.S. I'm using exactly the same set up on the 225g with no problems, so it's not a problem with the two-part mix.