Apply Foam Background on Running Tank?

[Keelay]

Originally posted by Tiggsy
you need to realise the foam is MASSIVELY buoyant!

you need LOADS of rock to sink even the smallest bit of foam.....i had 20kg lumps of rock bobbing about like boats in my early tests!

you MUST stick the egg crate to the tank if you go that way, there's no way you will hold it down by propping some rock against it.

also - be careful assuming coraline will keep the UV off it - it may, but that's a LOT of coraline! (mine is epoxy coated)

Yeah the buoyancy thing is the unquestionably the real challenge here. Gluing and wedging seem like ticking time bombs to me. Adhesives, epoxy will eventually fail. Magnets are decent idea, but they must be sealed so they don't rust. I've had quite a few mangnafloats break the seal and rust the enclosed magnet.

So My plan is similar to the thread posted earlier. Add weight throughout the structure.

Figure out the volume taken up by the amount of foam I'm going to apply. Assuming the worst, that the foam weighs nothing, then due to the Archimedes principle, the upward force will be equal to the amount of water it displaces.

So to counteract this force add at least as much volume of rock or sand to the structure. Since rock is typically 2 to 3 times as dense as water. It should overcome the upward buoyancy at around 50/50 proportion (rock to foam).

[badfish03]

Originally posted by Keelay
Very sweet thread. THANK YOU.

Are you thinking that the sand coating that the guy in the thread did would not be enough to block the minimal UV from my metal halides. I'm guess I'm a bit skeptical since the foam I suggested using is designed for using in creating outdoor waterfalls in koi ponds and such.

That plus the sand coating plus the minimal UV exposure is making me think that it's not going to be an issue. I know it's better to be safe than sorry. I will definitely let it "cure" for a while, before putting it in.

Its something that needs to be considered before adding this to a already established tank. The UV may be a non issue but coating with something that covers the intire surface and is more UV stable would help insure less chance of future problems.

[Keelay]

Yeah, just read the entire thread. I realized that the way to get the sand to stick is use epoxy as well. I'll probably do that. The hard part now is I have been wanting to implement a closed loop. I need to plan out the holes in the back and come up with an a nice aquascaping design that will blend well with my existing setup and shrouds the new cl plumbing.

[Fishbulb2]

Not trying to distract the thread but what about using agrocrete on the eggcrate lattice instead of the foam. I imagine that would get rid of your buoyancy issues? I use DIY agrocrete rocks instead of live rock, and they are covered with life. I think it would look nice, last longer, and be easy to implement on an existing tank. Also, maybe you could embed strong rare earth magnets into the foam (near the eggcrate and near the surface that will be towards the rear of the tank). Then you could use magnets on behing the tank to help hold the structure in place.
just a thought,
FB

[Cheekmonkey]

well if the eggcrate extends the full hight of the tank then something can be added to the top frame of the tank outside the water to keep the eggcrate from rising above frame level, and therefore holding the whole thing under.

[kraash]

Originally posted by Keelay
Nice work. It looks a million times better. Do you do that with the tank running?

Yes, the tank was running when I put them on. I had to test fit, cut a little more and test fit again several times. I used a coping hand saw that is commonly used for wooden trim work to cut the angles and curves to fit to the live rock underneath. Just rinsed it in the sink and back in the tank after cutting.