an upstream refugium is much better than a downstream refugium, most only do downstream as they cant fit the upstream above their tank or if they can, its an eye-sore. i have an in-wall tank so have contemplated putting in a small 180 litre upstream refugium above my display and having a portion of the return flow going to this. this would be specifically for breeding pods to gravity feed the main tank. im about to split my current (320 litre) refugium in half, either with baffles or egg-crate and have macro algae in the first half and LR/pods/frags in the 2nd half. there are certainly some types of caleurpa that are much more painful to keep than others. i think racemosa (which almost looks like weed with small grapes on it) is easiest as its large and easier to trim. grows extremely fast though. the smaller calerpa (smaller intertwining type) is stringy and if you get it growing into your live rock, you will never fully get it out. it sticks like s@#$ to a blanket! have a go with racemosa, it cant hurt - but as pies says run carbon to keep up good water clarity (or zeovit )