View Full Version : How to repair a center brace

07/24/2017, 06:19 AM
Hi all,

I have a 90 gallon tank that I bought 2nd hand. When I bought it, the previous owner had broken the center brace, and repaired it with thick, black cable ties. While it did the job, it was unsightly, and made the shadow cast from the brace even wider than the original annoying black plastic brace.

Fast forward 12 months, and after a 2nd outbreak of velvet (yes I do quarantine, and after the first outbreak, I left the tank fallow for a couple of months... but it reemerged), I decided a complete tear down, bleach the rocks and sand and start from scratch.

As the tank was empty, I decided it was time to fix the center brace. I wanted to replace the black plastic with something transparent, and I saw a picture online somewhere that looked like what I needed. I can't recall where I saw it, but attached are some pictures of my repair, so you can copy it should you want to.

It took me a while to track down the materials I needed for this repair. The material used for the brace, is 1/4" thick Lexan (a polycarbonate). I found the big box stores were useless for this, as they either wanted to sell a whole sheet of the stuff (at exorbitant cost), or only had fragile plexiglass. Plexiglass splits easily, and is difficult to drill. I sourced my Lexan from a local glass company, they just asked for the size I needed (2.25" x 17"), and cut it for me. The cost was $9.99, so not expensive. It pays to shop around your glass companies, as the same thing from another company was $16. It still doesn't break the bank, but that's $6 towards another fish! Remember, when deciding the length needed, it has to fit inside the tank.

I wanted to use nylon bolts, as I didn't want metal ones corroding, and releasing nasty stuff into my tank. I had trouble tracking these down, but eventually found them in Lowes. They are by a company called 'Hillman', and are 1/4-20 x 1-1/2 screws (written on the pack), 1/4-20 hexagonal nuts, and 1/4" nylon washers.

Before screwing this all together, I put some Super Glue to bind the remaining brace ends, to the Lexan.

I think the results are pretty neat, and no more shadow cast by that black plastic brace. I hope this helps!


07/24/2017, 07:16 AM
Nice job. FWIW - Lexan is plexiglass, just not the trademarked name. I have repaired several tanks that way over the years. What you did will last the lifetime of the tank.

07/24/2017, 07:45 AM
That seriously looks great good job !

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07/24/2017, 10:08 AM
Now fill it up and let us know when you shear the nylon screws in half :p

07/24/2017, 10:09 AM
Nice job. FWIW - Lexan is plexiglass, just not the trademarked name.

Lexan = Polycarbonate
Plexiglass = Acrylic


07/24/2017, 10:47 AM
Now fill it up and let us know when you shear the nylon screws in half :p
I'm kind of hoping the nylon holds, helped by the Super Glue... I will post to this thread if they fail though.

07/25/2017, 09:15 AM
Nice clean job.
I did something very similar on a 55 gallon tank that the center brace was melted in half.
I used nylon bolts as well.
That was 3 years ago, and the brace has held up.

07/25/2017, 10:26 AM
Looks like a good repair. I'd probably have used SS bolts (nylon ones can shear), but I'm OCD that way :lol:

07/26/2017, 10:14 AM
I think your repair looks nice and clean, but why take the risk? 90g is a lot of water. Also how old is the tank, just my opinion it would cost quit a bit to clean up and repair damages it may cause if the tank fail. New tanks can fail too but knowing this old tank has already been compromise, I would always be wondering when is it going to fail.

07/26/2017, 10:38 AM
aznflyfisherman, I understand your point but it also seems counterproductive to a DIY forum.

That said I would like to offer my own specific feedback. Nylon fasteners are (by design) not as strong as other materials but I don't think there's nearly as much pressure on these parts as we may think, so it'll probably hold. At least, initially.

I would be worried about long term for two reasons. First, nylon hardware degrades rapidly with exposure to UV. Most reef lighting emits at least some UV so it's something to consider. This is easy to solve though by shading or painting the hardware.

Second, nylon is somewhat hygroscopic (it absorbs water). Once this process starts, it loses strength rapidly. A fish tank is obviously not a good place for a material that gets weak from water exposure. Again though the good news is you can solve this by protecting the hardware.

Cliff notes: paint the exposed nylon a dark color and keep an eye on it.

Stainless is an option but I think I'd paint stainless too. Threaded fasteners are a worst case scenario when it comes to corrosion resistance in stainless, thanks to all those acute angles in between the threads.

07/26/2017, 11:13 AM
I did the same thing to my 112 about 10 years ago. Still holding fine :)

07/26/2017, 12:02 PM
I did the same thing to my 112 about 10 years ago. Still holding fine :)
Did you use nylon screws as well Andrew?

07/26/2017, 12:41 PM
Did you use nylon screws as well Andrew?

They will more than likely be just fine..
I was kind of just messing with ya..

07/26/2017, 04:41 PM
Did you use nylon screws as well Andrew?

Yes. Perfectly safe. I hardly was the first person doing this in 2007 or so and I'm sure some of those tanks are still going too. It was when I switched from MH to T5 I had to do something about the center brace shadow. I know it's the cheapest way to make tanks but it sucks there are so few standard stock tanks that have other bracing alternatives. Obviously rimless is way more money, but how much more could it possibly cost to make them with clear plastic / acrylic.

07/27/2017, 08:34 AM
I suspect the nylon screws would be fine, but as there is still no water in the tank, I decided to replaced them with stainless steel screws. Thanks for all the feedback!

07/27/2017, 10:52 AM
I'd consider painting or coating them if you haven't yet. Even something like plastidip. I don't think it's likely that they'd fail from corrosion but you may be disappointed if they look ugly after a few months and then you're stuck like that. Easier to address now.