These seeds were put in around March.  I also  use an old cake container.  I fill the containers about  two inches deep with my Aquaponic basket mix. The mix is very loamy, so as to let the air circulate through the mix keeping it aerobic.   I also wet the mix, but not saturate, just a feeling of dampness. The general rule is put the seed in as deep as physical size.  I will generally take a hand full of my mix and lightly sprinkle all the seeds putting a little more on the bigger ones and a little less on the smaller ones.  This creates the depth continuity.  Lastly, put a lid on either tight on or with an air gap if theres high humidity.  After a few days you will start to see some of the quicker germinating seeds show their heads.  The mix can also start to dry as the seedlings start to emerge.  I take a spray bottle and ever so lightly give them a quick water spray or depending on your judgement and experience spray a light compost tea.  When the seedlings are up and running I put them out doors  in the nursery raft area ready to go into the main system. Cold nights can make germination somewhat unpredictable, however indoors with controlled temps can sometimes yield more consistent results. Most of the crop that is in the system at the moment has been germinated much the same way. In fact it is really surprising the amount of seedlings that appear making a lot of transplants to an Aquaponic basket.  The good news, you know how many plants you are dealing with so you can more accurately project the yield.