Never buy a very large glass aquarium.

[Stan510]

Yes,you can even bolt acrylic tanks together. Viktor of Florida Fish rescue combined two acrylic tanks,one was 800 gallons and the other 400 hundred and glue welded and like you asked,used bolts to put them together. It works and he has a mega sized tank out of two aquariums that are not even the same height or width..not kidding. Just look at it on youtube.
My 240? My cousin when he was in his mid to later 70's and I moved it empty. He weighs like 140 pounds..a thin guy.
Youtube has many vids of glass tanks busting. The 400 gallon reef was near the worst,but plenty of others.
He was so disgusted..just gave up on reefs for awhile I imagine. The whole filter,chillers,multiple pumps,reactors,extra huge water containers..all that took up a room below the tank. Ohio Fish Rescue vid. Forgot to mention it. Even then,OFR said they were not going to repair the tank "Once they blow,not any good anymore"..they just wanted the glass as front on any future building projects.

 

[Utar]

I have read several times on different forums where people's acrylic tanks have started to bow out under the strain of the water. I can't vouch for it personally, never owned one.

 

[madmark285]

I have read several times on different forums where people's acrylic tanks have started to bow out under the strain of the water. I can't vouch for it personally, never owned one.

Yep, the advantage of acrylic is it can bend, the disadvantage is it will bend or bow.

 

[madmark285]

And I imagine with acrylic it should be possible to put screws or pins into the joints to supplement the silicon.

Acrylic tanks are welded by using a solvent that melts the material. Silicone does not adhere to acrylic very well.

 

[madmark285]

Hmm... Only wondering since I'm going to be cheeky and ask for a 5-6ft tank for my birthday, but my parents have already (understandably) voiced their concerns about the floor caving in lol. I wonder if an acrylic tank would put less strain on the floor than a glass tank.

Cut&paste time:
"A 55-gallon tank weighs about 42 pounds when made of acrylic and about 78 pounds when made of glass, "

Now fill it with water, it weighs about 650 pounds (294 Kg).

For second floors, find a spot along an exterior (outside) wall and better yet, the tank is perpendicular to the floor joist. Should be no problems handling the weight.

I put a 75 gallon tank with sump in a finished attic space with no worries. Plus I have insurance

 

[PlasticGalaxy]

Cut&paste time:
"A 55-gallon tank weighs about 42 pounds when made of acrylic and about 78 pounds when made of glass, "

Now fill it with water, it weighs about 650 pounds (294 Kg).

For second floors, find a spot along an exterior (outside) wall and better yet, the tank is perpendicular to the floor joist. Should be no problems handling the weight.

I put a 75 gallon tank with sump in a finished attic space with no worries. Plus I have insurance

Ooh, mind if I send this over to my parents to make a compelling case?

Both of my tanks are up against the exterior wall right now, actually! So I've got that going already!

 

[Stan510]

I also meant to add that my 240 is perpendicular to the floor joists so it's like six, 4x6" beams are holding it up compared to half that or less, if I set it up against a wall. I also put plywood down over the floor to further spread out the weight.
I know anything can break if treated really bad. But,The Dubai Mall's one million gallon aquarium of 6" thick acrylic or even more..sprang a leak. They repaired it no problems in fast time. Glass? Oh boy, the Red Sea parting would be only the bigger event..
In 50 years I can't name even one single plastic tank that ever sprung a leak for me. Glass? I don't even want to calculate..

Bend? eh. They never break is much more important.

 

[PlasticGalaxy]

In 50 years I can't name even one single plastic tank that ever sprung a leak for me. Glass? I don't even want to calculate..

You guys are worrying me! I'm only four months along into fishkeeping, and I'm already worrying about switching to acrylic!!

 

[Colin_T]

I've never heard that. Why should tanks be rimless over a certain size?
Thanks.

You just don't need it with small tanks.

-------------------

I have read several times on different forums where people's acrylic tanks have started to bow out under the strain of the water. I can't vouch for it personally, never owned one.

Perspex/ Acrylic and glass tanks can both bow outwards if the glass/ Perspex is not thick enough or if the tank has no supports and cross members on top.

It happens quite a lot but they usually only bow out a couple of mm so it's not normally noticeable.

-------------------

You guys are worrying me! I'm only four months along into fishkeeping, and I'm already worrying about switching to acrylic!!

Don't worry about it. 99% of fish tanks last 20 years before they start leaking, and some last longer. I had tanks that were 30 years old and still had the same silicon they were made with.

If you are concerned, just monitor the silicon. If the silicon turns cream/ white, or becomes really had and no longer feels firm but slightly squishy, or if it gets small bubbles in, then it's time to worry. But not until then.

 

[madmark285]

You guys are worrying me! I'm only four months along into fishkeeping, and I'm already worrying about switching to acrylic!!

Price out small acrylic tanks A 29 gallon SeaClear Acrylic Aquarium Combo Set is $258 in the USA. My LFS sells 75 gallon framed tanks at cost, $100.

For tanks about 100-150 gallon and up, start looking at acrylic. Long ago I worked in a aquarium store that had one room will all acrylic tanks, I love the rounded corners. Building an acrylic tank is on my bucket list.

 

[madmark285]

Ooh, mind if I send this over to my parents to make a compelling case?

Both of my tanks are up against the exterior wall right now, actually! So I've got that going already!

Go ahead but you should just ask your Dad, " Where are the load bearing walls to determine which way the joists are running?" That should impress him.

Floor joist will run perpendicular (90 degree) to the load bearing walls ie: the joist sit on top of the wall.

 

[Stan510]

Oops.meant 2x8" beams.
Again going over 75-100 gallons in glass is a real risk. Zero risk in Acrylic from a major long term company.
That king of diy on the Tube? his builds are all acrylic. Tanks with just one pane he might have done in glass.

 

[StevenF]

Weird hypothetical question here, but if you were to have an acrylic tank in an upstairs room, would it put less strain on the floor than having a glass tank of the same size?

90% of the weight of any tank is due to the water substrate and decorative rocks and wood. So overall the So overall the material of the tank does really matter as far as the floor is concerned.

At this sight the weight of a 100 gallon tank is listed at 831 lbs for glass and then 786lb for acrylic. The difference of 45lbs doesn't mean much to the floor.. Also if you fill the tank with salt water you add another 19 lbs.

It is my understanding that a American home second story floor its designed to support 40lbs per square foot. I don't know what the standard is for the UK.

 

[madmark285]

It is my understanding that a American home second story floor its designed to support 40lbs per square foot. I don't know what the standard is for the UK.

I am not sure if a generic 40lbs per square foot makes sense from a engineering view. Take one standard overweight 200 lb American standing on the floor, that's 5 times over the load bearing capacity of the floor.

If the load on the floor is next to a load bearing wall, the capacity of the wall would be a critical factor. Move the load to the middle of the floor, the load capacity of the joist at their highest stress point would be the primary issue. Worst case, an aquarium sitting above one joist in the middle of the span. Rotate the tank 90 degrees, now the load is distributed over multiple joist.

I put my 75 gallon tank in the third floor attic, it sit directly above a load bearing wall. No worries for me.

 

[Slaphppy7]

90% of the weight of any tank is due to the water substrate and decorative rocks and wood. So overall the So overall the material of the tank does really matter as far as the floor is concerned.

At this sight the weight of a 100 gallon tank is listed at 831 lbs for glass and then 786lb for acrylic. The difference of 45lbs doesn't mean much to the floor.. Also if you fill the tank with salt water you add another 19 lbs.

It is my understanding that a American home second story floor its designed to support 40lbs per square foot. I don't know what the standard is for the UK.

"Also if you fill the tank with salt water you add another 19 lbs."

???

100G of water weighs about 834 pounds....