I haven't used lanthanum in quite some time, I bought my lifetime supply quite a few years ago from a pool supply store.
I used it weekly for probably 6 months with a Kole Tang in my 90 gallon. I didn't see the Kole have any issues when used. Dripped it very slowly into a 5 micron sock, it was like a drip every few seconds into the sock. It would take 8 hours or more to drip the gallon of solution into the sump if I remember right.
My tank matured or whatever, no need to use it right now, however I'd use it in a second if my phosphates got out of control.
What are you using to measure your phosphates? Phosphorus Ultra Low Range Colorimeter HI736 Hanna Checker is what I've come to rely on. There has been some confusion on the right checker. I prefer this one, there's a simple conversion formula you can use.
Take the number you get from the HI736 Hanna Checker, Multiply it by 3.066 then divide by 1000. This gets you the PO4 in ppm. Example 20 on the Hanna gives you 0.061ppm.
Hope some of this helps someone. I was so confused several years ago, I had the wrong Hanna Checker, I was so frustrated I almost gave up on the whole thing. Hanna does have a new checker that does the math for you, the 774 I believe.
Many people complain about the powder packages for the Hanna Checkers, if you simply follow the printed dotted lines and make the curve on the packet, you'll have much better luck.
Take care all.....