custom tank/rebuild from old 75gal. + driftwood from florida 4 sale

It can be done.  It WILL be a challenge, but it can be done.

The plywood will need to have multiple coats of Bondo-the automotive fiberglass resin-applied to make it water tight.  This needs to be done outside in a very well vented area as the fumes will quickly over power you.  So this is a summer project to say the least!  You will have to have the plywood cut and screwed together before you can use the bondo.  Also, make sure you use the fiber glass reinforcement cloth at any and all seams/corners.  I have seen several tanks built out of plywood and have been part of building many large vats/sumps this way.  Assuming the tank is on a well supported stand and isn't moved it MIGHT last 5-6 years.  I've had vats last as long as 8 years.  Most fail after 3-4 years though.  Wood just isn't a stable enough material to coat with resin and to silicone glass to it and have it not end up cracking the sealant or silicone as the wood expands and contracts.  Just ask any wood boat owner how much time they spend working on their boat versus using the boat.  It's a labor of love to say the least!

Using several panes of glass to create a single viewing pane is a whole new challenge.  I'm assuming you are building a plywood front to the tank that each piece of glass will fit into?  Sort of the "porthole" effect but on a larger scale.  Try to track down a single piece of plywood the length of the tank you are building.  You will need to seek out true lumber yards for this.  It will be expensive!  The 2 big problems will be A) Keeping the front and back runs of plywood from bowing very badly.  Lots of braces across from front to back will be needed.  Any bowing as the tank is drained and filled will lead to cracks forming in the bondo or leaks forming at the silicone seams around the glass.  A 8-12 foot plus run of glass held in place around plywood will create all sorts of difficult structural issues in terms of weak points (pressure or stress points).

But if this was easy everyone would be doing it!

And just look for 100% pure silicone.  Make sure there are no mildew inhibitors or the like.  I believe it's GE window and door silicone that fits the bill.

Good luck and take your time!  And don't forget to figure out how you are going to get the tank from the construction location to the set-up location.  Long tanks are really hard to move with out beating the tank and your home up!

Jeff

I have resealed a few tanks and it was not fun - unless you really like to be overwhelmed by the smell of vinger.  That being said from what I have seen online plywood tanks in the long run dont work out so well.  If it were me I buy a glass tank and sleep better knowing that it should not leak

I hear ya.How about the better brands of silicone that members have used in the past that have worked for them?I was planning on using doubled 3/4inch plywood for the remainder bottom and rear panels.

Three panes to make one front pane of a tank? Not such a good idea. It can be done, but I would highly advise against it. The margin for error on this portion of the tank is very small! Any flaw in a tank of this size could end up turning your room into a pond.

It also appears that you have zero to minimal planning complete. A project like this takes months even years to plan and execute properly. There are many expenses that can and will pop out of nowhere on a project like this. Have you thought about how you are going to seal the tank? How about filtration? Lighting?

Just a few thoughts!
Keeper

Ur plans for the tank still dont make sense at all. U have 3 sides....last time i checked it takes more then 3 pieces of glass to make a tank.....i dont see how this can be done at all!

got an old 75 that pooped at a corner and is in the workshop disassembled. thinking of using the three large panels as stricly the front panels and making a 12foot long tank or maybe a 4x8 'L' shape. Anyone done something similar? I know the pressure factors have to be considered, and I have seen larger tanks with extra panes of glass used as support inside them at the top. HELP!!! Wife says the clock for the tank is ticking and to either s@#t or get off the pot. I also have and can get some killer large (1.5 to 3foot) peices of driftwood. Mostly mangrove(red and black). will post a pic of mine soon.