The reason that only one compound was able to be tested is in part due to the difficulty of getting the starfish to attach to the mussel lines, and in part to the difficulty of creating mussel lines with densities high enough to encourage starfish attachment.
The original set of mussel lines obtained were not very dense, and the starfish did not attach to them strongly, or in high numbers.
The second set of mussel lines were better at recruiting the starfish, and were the ones used in the calcium hydroxide trials, however the mussel sock material was not very durable in the conditions of the tank, and began disintegrating after a week in the tank.
These lines also used mussels bigger than would be desired.
Two attempts were made to simulate spat collectors using much smaller mussels, along with Christmas tree style mussel rope, but these mussels died before trials could be carried out.