The finer silica is more likely to blow around and won't hold plants down very well. When you vacuum the substrate it will be more likely to get sucked up, whereas the larger grained is more likely to NOT get sucked up. Remember to hold the tube at an angle when you syphon so the sand can drop back down easily. Sorry, but I would stick with the larger grained silica pool sand, it is the best inert substrate I've used.
Best regards,
Harriett