Not sure about tips or tricks, but can perhaps just give some general information that was told to me by a lady in our aquarium club.
She kept a log for over a year of her Spider Sponge, as they are hard to keep. I can only recommend that you do the same to follow up on your sponge's progression.
Summary of her log - will refer to the Spider Sponge as "The Sponge":
- Flow: The Sponge seemed to prefer a strong flow, but not aimed directly at it. The Sponge thrived most with changing flow and seems to prefer a horizontal stream, rather than a diagonal one. Avoid upwards pushing flow.
- Food: Had the best results with phytoplankton. When The Sponge grew, I could occasionally feed small mysis, larvae or other types of food that fits. However it seemed to be healthiest with the plankton. Take special attention when feeding other corals or creatures that the flow does not carry bigger food parts in The Sponge's direction, as the pores can get clogged.
- Water: The Sponge started to "wither" with Nitrate levels higher than 15ppm. As such I kept nitrates lower than 5-10ppm at all times.
That's what I can remember from it really. Not much but yeah... Wasn't really so interested in that one tbh, as in no way am I prepared to keep one (yet).
Good luck with it and would love to see a log with pics sometimes