transplanting from rockwool to tank

hi can anyone help!i currently have 2 seeds which have sprouted in rockwool and i want to transplant them from the rockwool plugs into bigger cubes.at what stage do i do this? and when does the process begin when i want to put them in to the tank with flowing water and nutes?can any one help?cheers

If they have literally 'just sprouted' then give them a week to grow some roots, then put them inside another bigger cube and put them in your table/tank.