Have you tried putting a big rock on top of it?
Sorry sorry. Styrofoam castle is sort of the opposite of a planted tank, so you're going to get a little teased here.
I can't think of anything discrete that you could use to weigh down that much styrofoam. For weigh-down options, you'd have to put something quit heavy under the arch of the castle, but that would mess up the look you're probably going for.
I'm surprised silicone didn't work. Have you tried really sobbing it on thick? My advise would be just retry the silicone, but really go nuts this time.
Sorry sorry. Styrofoam castle is sort of the opposite of a planted tank, so you're going to get a little teased here.
I can't think of anything discrete that you could use to weigh down that much styrofoam. For weigh-down options, you'd have to put something quit heavy under the arch of the castle, but that would mess up the look you're probably going for.
I'm surprised silicone didn't work. Have you tried really sobbing it on thick? My advise would be just retry the silicone, but really go nuts this time.