Escape proof tanks

[Oceanic Art]

I am new to owning an octopus and in the process of setting up my first tank to house my new pet. I bought a Red Sea Reefer 250 aquarium (55gallon) with a built in skimmer and pumps that all operate through a downflow system. The top edge of the tank is glass with no need to run pipes, hoses or wires through the top. My question is, if I affix a piece of acrylic (like plexiglass, although thick enough and not prone to warp) should I drill holes for air, if so how much? Roughly what size is the max size of an air hole I should consider without knowing the exact species (I've read the section on what the local fish supplier will know about the species, and yes, it's a "common octopus" "probably from Bali". This tank top that I'm considering will sit flush against the top of the tank with weights around each corner to prevent a strong octopus from lifting the top, please advise if you don't mind. I'll post a picture of the tank as it sits right now without the top
Thanks
Scott

 

[DWhatley]

Scott,
We opt to drill holes in our lids (Here is one that we drilled). We used a peg board as a template and a sharpie on the plastic film liner (that peels away) then drilled all the holes where the marks indicated. I suggest sizing the holes so that a bamboo skewer will snugly slide through (for occasional cleaning). Keep in mind that the water side will be cooler than the top so you will get some warping even with very thick acrylic. Keeping weights on at least the 4 corners at all times will go a long way to minimize the warping.

 

[Oceanic Art]

Ok perfect. My other thought was to use a hardwood frame and screen (same principle as a screen door). I'm just unsure of how much oxygen flow is needed, I can for sure see this lid sweating and warping so maybe the screen door type lid would be better? If I do this I will make sure the edge of the tank sits inside the frame so there will be contact with the frame on the entire top edge of the tank as well as the sides. If you recommend this way I will scrap the acrylic lid and make something like this. Thanks for your help and I'll be sure to post a pic of the lid once I'm finished

 

[sirreal]

Stick with the acrylic. I made one out of a 1/4" mesh and it worked great but my octo would come to the top and spit water at me to get my attention. You would be amazed to see how much water a decent size octo will put on the floor and all over the wall lol.

 

[DWhatley]

I definitely like the acrylic and use it on all my tanks but I wanted to warn you about how and why it warps. I have experimented a little with fiberglass screen and am not fond of the ease the aluminum frame twists so have not used it on a tank.

 

[Oceanic Art]

Yeah I hear you about the warping. I may only use it temporarily as I've already purchased it. I may use weights (some beach rock etc) will look kind of cool. Maybe I'll build a frame from hardwood that I can epoxy to the edges that will hug the sides of the tank as well. This may not eliminate the warp over time but it will slow it comsiderably. The story about the octopus squirting water doesn't make me not want to use screen tho lol