Foundation for outdoor aquarium

Adam,

You could:

Using some 12" diameter "sonotube", dig four holes and place your new concrete "piers" down 30" below grade for frost depth.  You could cast Simpson column bases in the concrete for 4x4 treated supports (I'm sure Home Repo carries them) and reinforce the concrete piers with 4" square metal fence grid, lapped together a good half circle.  Using post concrete mix, you could have a very sturdy platform! 

Unless you're talking about mud that you sink a foot in when you try to walk in it, soils shouldn't be a problem for that much weight, as long as you have something solid under it.  Your vehicle more than likely would put more pressure on the soil than a 180 gallon tank would on four supports.  It's all about spreading the load out.

I'm still baffled as to why you want a tank outside (no offense!).

The approach you already have will probably work as well.

Corey is this what you mean.  Im not sure I understand how to use the square metal fence grid.

Adam,

Yes, that's more or less what I meant.

The square metal fencing is reinforcement for your pier/footing to help prevent it from cracking.  That's it!  You just make a hoop out of it, lift it up when you get concrete in the tube, and keep it 2" away from any side- so it's a tight hoop extending from the top to the bottom but "floating" in the concrete.  You aren't talking about loads that would really require real building code-required reinforcement.  You bring me somebody that would argue that to the contrary and still be reasonable, and I'll be surprised!

The sonotobe is just a form- you don't need it if you're trying to do this cheap and you keep the soils from spilling back in the hole.

If you're not worried about it ever freezing, the previous approach may be less expensive and easier if you don't want this to be hard to remove.  After thinking about it, if it did freeze, frost heave is probably not as big a deal as a cracked tank!  So 30" may be extreme overkill- just dig to the hard clays.  One other thing the concrete sonotube pier does is prevent rot of the wood since you can get it above the soil 6" or so.

Thanks. You guys are great!! 

Since two pillars will only be 12" apart, could I just dig one large hole for two tubes and fill them at the same time? Also, since it will not freeze, could I do a 20" deep hole?

So I build the stand (with the column bases attached ) and somehow support it EXACTLY where it will be over the holes. Then fill the tubes with cement.  Adjust the stand if needed to make sure its level and let the cement dry around the column bases. Is this right?

When you get ready to do this call me

That is exactly what I was thinking.  I was thinking "Hey Adam, just tell Chris you'll give him a couple frags if he does this for you". 
I'm sure someday I'll be building one of these in my backyard and that has always been my plan.

Adam

Chrislc-

You're right- the sketch would give you more footing, and it's not too hard to build.

Adam-

Post-hole concrete (the pre-mixed stuff) is not high-strength concrete at all, but it should do fine for this.   Sounds like a sweet deal for Chris to come help, though, if you've never done this before.

Just don't build some pole-shed using these piers, ok?

Happy to help!  

one thing I was thinking about... Sorry for the late chime in.....

We built a 18'x18'x8'vaulted greenhouse. We used treated railroad ties as the base and anchored them all together with BIG lags. I have seen pine break at the bace of the concrete with a load shift.

What is the point in a 180g 1500lb ish aquarium outside in a greenhouse? Why not go with a pond? Trust me I have a 225 catfish tank.... I have thought about it....

oh... and fibercrete is awsome....

What is the point in a 180g 1500lb ish aquarium outside in a greenhouse? Why not go with a pond?

Its hard to enjoy a salt water tank when you can only look at it from above water, dont you think? I guess I could always get my mask and snorkel out.

The whole system will be 500+ gallons. The 180 is just the display portion of the setup.  The rest of the water will be in several large 100+ gallon rubbermaid stock tanks.