Recommendations on how weigh this polycarbonate lid down

[Irecruitfish]

3 Polycarbonate lids across this 210.

I just lost a fire eel in an quarantine tank 2 days ago but that's a different situation as I should have weighed down the lid more properly. My mistake but don't want to make any mistakes on this one.

So far so good in this tank no one has popped up a water bottle. However I have a 24" fire eel in here and it's getting large rapidly.

I was thinking about laying a 2x4 across the top but any other ideas?

 

[altums85]

Attach some velcro to the top of the tank and lids. 2x4 works too but looks ugly and bulky