How many lbs of hardscape can an aquarium bottom support?

[Caperguy99]

I have a 210 Aqueon arriving on a pallet to my home this week.

I’ve washed and prepped around a dozen metamorphic rocks for use in the tank. Some of them are big, and they are all very heavy. Altogether, the rocks likely weigh a few hundred pounds. I planned to lay down eggcrate, then the stones, then around 240 lbs of substrate sand. I have a photo of my desired setup with the rocks below.

My LFS seems worried about how much weight in hardscape I’ll have in the tank. They want me to reduce to just a few smaller rocks, but I’d like my African cichlids to have some caves and such.

So my question is: do you think this would be too much weight on the bottom of an Aqueon 210? The absolute last thing I need is a bottom blowout. Does anyone have experience with this sort of thing?

 

[Sassafras]

How will the bottom be supported? If on a solid surface with foamboard or other appropriate type pad, I would feel more confident than on a perimeter support only type stand.

 

[jjohnwm]

Interesting question, one that has never troubled me over the years. I have, even back in my all-glass-tank days, filled plenty of my aquariums with far, far more rockwork than you are showing here...I'm talking easily 4 or 5 times as much, maybe more. The tank bottom is already supporting the weight of 210 gallons of water, let's say roughly 3/4 of a ton. Adding a given mass of rock doesn't actually increase the weight by that mass, since you still have to subtract the mass of the water that has now been displaced. So your total mass will be a paltry few hundred pounds greater than just the tank full of water.

Now, admittedly, most of my tanks were back in the day when manufacturers used glass considerably thicker than what is seen today, with a significantly higher safety margin. Nevertheless, even with today's flimsy aquariums, I personally think that you have nothing to worry about. Liability is a harsh mistress; I don't believe manufacturers can take the chance of building tanks with such a narrow safety margin that you can't add a few rocks and some sand.

But, of course, most of my tanks are in my unfinished basement...and this isn't my tank...so YMMV.

 

[sokolis]

I've seen glass reef tanks with hundreds of pounds of live rock and never saw a blow out.
I'm not scientists but id imagine the rocks aren't as heavy once filled with water as well
Just My opinion and what I've seen in the years I worked in a lfs. I'm specifically talking glass tanks

 

[Ogertron3000]

Here’s a tank I set up recently, it’s a 3 foot40G. A lot of rock in it , no idea of the weight it it’ would be pretty heavy.
I was going to add more on the other side but I got a bit nervous and decided not to.
Do some googling and you will see plenty of tanks stuffed full of rock, I think you will be okay but it’s really up to you. Don’t do it if you will e stressing about the tank bursting or you will always be on edge.

 

[Caperguy99]

How will the bottom be supported? If on a solid surface with foamboard or other appropriate type pad, I would feel more confident than on a perimeter support only type stand.

It’s the Aqueon stand that comes with the tank, which I believe is a perimeter support. This is exactly the concern my LFS raised - they said a flat bottom would be able to support much more weight.

I’m getting some mixed feedback - with some saying it’s absolutely fine and others expressing some concern. At the end of the day, I suppose better safe than sorry - though if anyone has exactly this tank, the Aqueon 210 glass, I’d be chuffed to see some photos of how much hardscape they’re using.

 

[FJB]

I've seen glass reef tanks with hundreds of pounds of live rock and never saw a blow out.
I'm not scientists but id imagine the rocks aren't as heavy once filled with water as well

Although the above is true, the actual weight of live coral rock is way, way less than the weight of a comparable mound of metamorphic rock as shown in the first pictures. Also, the metamorphic ‘fill’ with water much less, in fact very little. One possibility is using lighter rocks below, or even synthetics, in places where they cant be seen, thus reducing overall weight. And finally, the overall structure needs to be super stable. No rock falling can be risked. Good luck.

 

[Caperguy99]

Although the above is true, the actual weight of live coral rock is way, way less than the weight of a comparable mound of metamorphic rock as shown in the first pictures. Also, the metamorphic ‘fill’ with water much less, in fact very little. One possibility is using lighter rocks below, or even synthetics, in places where they cant be seen, thus reducing overall weight. And finally, the overall structure needs to be super stable. No rock falling can be risked. Good luck.

Thanks for this - I’ll take out the largest rocks and try to make a few smaller caves with the littler ones. This way I won’t be worried.

 

[RD.]

You could potentially fill your entire tank, with those rocks. Yes, stacked to the brim. lol

How strong is our glass tanks and can withstand the weight? | MonsterFishKeepers.com

Just ensure that there are no pressure points directly on the bottom, as the bottom of that Aqueon will be tempered glass.

 

[RD.]

Also, no need for egg crate unless you have sharp pointed areas that can create pressure points on the glass. I've never used egg crate under boulders, I just ensured that the boulders were smooth/flat on the bottom.