Honestly, if you're not going to go with nudibranchs, I think that the only effective killing method is injecting the bases or mouths with scalding/boiling water: @Tamberav's solution (thanks!). I use the syringes from Aiptasia-X for this purpose, and it's certainly the best thing about that product.
I ordered four nudibranchs in August, and then cultivated them in a jar (for quarantine) with aiptasia-infested macro until they bred and laid eggs. I then transferred it to my display, and they've just about completely cleared out my RSM250. I'm now transferring the nudis to two other, smaller tanks that have aiptasia as well.
I ordered four nudibranchs in August, and then cultivated them in a jar (for quarantine) with aiptasia-infested macro until they bred and laid eggs. I then transferred it to my display, and they've just about completely cleared out my RSM250. I'm now transferring the nudis to two other, smaller tanks that have aiptasia as well.