Lettuce question

[stuartambient]

I finally got my first hydro gardening experiment up and running. Basically an aerating bubbler system. It has 9 pots in a styrofoam raft and 480 wequivalent Full Spectrum cfl's (across 2 bulbs)

I used Rapid Rooters which fit quite nicely in the 2" net pot. Now , I was under the assumption that 60-70F was good temperature with a drop down to 55F at "night". What I didn't consider was the germination process. Now I read somewhere that lettuce germination should take place with water temps in the 40's.

1 plant has emerged with some tiny little strong looking leaves. I can see a few other seeds that are morphing. A few others are too difficult too see due to the depth of the Rapid Rooters. I'm wondering should I drop the water temp down ? I've been maintaining it was an aquarium heater. Otherwise the natural temp is about 60F.

This is now the 4th day since planting.

TIA
Stuart