Gracilaria - My current home culture setup.

I have purchased a clump of gracilaria macroalgae to feed my hippo tang.
What I did was tie a small clump to a small piece of rubble and dropped it into the aquarium. I then separated the rest of the gracilaria and also tied them to small rubble and kept them in a separate grow out bin.
The bin is just a shallow plastic bin with a small powerhead and a curly PC bulb above it. The new growing tips are very delicate and can break off easily so I need to use a very low flow powerhead.
I use old water from my display tank as the "new" water for the gracilaria bin, and toss out the old water.

Here's a picture of the growout bin in my garage.

The hippo tang loves to nibble on the young tips of the gracilaria, but leaves the thicker stems alone. So after a while, the gracilaria in the tank ends up being a bunch of stubs.
When this happens, I take out the stubby gracilaria and toss it into the growout bin and put in a replacement clump into the display tank.
I rotate new clumps approximately every 3 days.

So far it has been going great.
I have not used any fertilizers yet. It seems like the old water from the display tank feeds the clumps just fine.
The only issue I have observed so far is that the water in the growout bin seems to get slimy (clear, but a little snotty) if I do not stay on top of water changes.
I am not sure if this is due to some form of sap being secreted by the gracilaria or some other biological buildup.

I also set up another bin outside, under partial shade just to see if the gracilaria outdoors would have a better growth rate under sunlight.

So instead of paying $10-$15 a month for fresh macroalgae to feed my tang, I now have a regular renewable supply right in my garage.
I am researching other easy to grow macroalgae that I can culture as well so that I can mix up the algae diet a bit.
I am still trying to fine tune this setup.
So far my biggest issue is still the slimy water. If I do not change out the water after three days, the water's surface starts to develop a thin and slimy film.
I am not sure if this is because my growout bin is not large enough, or if there is too much flow which injures the plants and causes them to secrete slimy sap.

I might move the gracilaria to my 50 gallon frag tank. At least that tank has a working skimmer which could deal with the slime.