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[Journal] Polishing/reinforcing an acrylic 100g tank for an oscar!


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Hi guys! This is still a work in progress but figured out I could post this here in case anyone is wondering how to polish/restore an acrylic tank. This was the first time I've ever done anything like this and it's my first acrylic tank (and it's big!), and after much research in old forums and asking around, I ended up with this result. I'm pretty satisfied with the result! It was a learning experience!

I bought this SeaClear system 2 100g acrylic aquarium for $150, complete with the stand and canopy (I ended up discarding these though.)

As you can see, the tank is extremely dirty, scratched and hazy, it seems it wasn't used for quite a bit of time.

Came with these ugly discolored gravel lol, no way I will be using that!

It seems to be a really old school type? It comes with the original bio balls used for the back, sump-like compartment as well as the pump, can't beleive it still works! Dude had it outside in straight up desert climate. I might have to change that in the future.

The background integrated sump. It had crusted up mulm and some rainwater lol.


A quick hosing to do a general cleanup.

Wet sanding the scratches

End of the first day, you can tell by my fat guy "OOF" that I was tired as hell haha. It was a killer arm workout.

Must polish until you achieve a frosty looking acrylic. I used 400 - 800 - 1200 and 2000 grit, but you will get better results if you use a wide variety of numbers! The amount of work you have to do also increases though. I did 2 sanding rounds with each grit. I bought that small sandpaper holding thingy at harbor freight, for $5. It definitely made the work much, much easier to be able to comfortably sand. 

Tutorials said you could use an electric sander if you want to do the work faster and easier for you, but you have to be careful not to electrocute yourself, as you will be using water with these sanding papers. I did not have one and decided to do by hand. Get someone to help you if you can lol, my uncle helped me with all the process so it took me less time than if I did it alone. You could get the whole family to help out one weekend! They will feel proud when they see the beautiful aquarium all set up for sure. Or get some friends, some cold beers/snacks and sand away lol!
After 3 days of sanding, it was time to polish the acrylic. I used Mother's car headlight polisher, along with a drill and a polishing bonnet with drill attachment:

The bonnet was $9 at harbor freight, but it ended up breaking! I guess the heat of using it too much obliterated it. I suposse they were made for a quick headlight polishing, not for a giant 5ft. acrylic tank lol!

We ended up moving to a buffer instead of the drill. It had more power and was more comfortable to use.

Felt the Mother's polishing cream wasn't enough, so I bought a Novus polishing kit.

That did the trick! I achieved this result with it:


Now with custom made stand. I felt the one that came with it was too flimsy. We did one with multiple 2x4's. Can't take chances with 100g of water and a huge oscar in earthquake prone area! (Baja California, Mexico, close to San Adnreas fault lol.)IMG_20200626_175010.jpg.6c4b0060a9c4a1acb5ee6b996c05f4c5.jpg


Now I need to finish up the stand (needs doors and paint) and I need to purchase a few pieces of the sump system that are missing. It seems it uses a "drip tray" of some sort to "rain" down water onto the bio balls below! It is a wet-dry filtration system, I have never used one of these, not even a regular sump, but it will be a learning experience as well!

The guy is anxiously waiting for his new, forever home to be finished!


Stay tuned for the next round of work! I need to complete the stand, (paint and doors) and reinforce the acrylic seams with Weld-On 40 acrylic cement!






Edited by HenryC
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Everyone should do this once, so they can appreciate the true value of a non scratched acrylic tank lol. It can be brutal when you have to be inside one. I've done a 180g before, you sweat so much being trapped inside working.

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I had the seam in my 100 gallon go in 2019 and I've had the materials to fix and polish it since at least Christmas but have been dreading doing all that again. Once is enough, can't believe how much work goes into that kind of project. Kudos on the results and documentation, well done. 

I really have to get around to finally fixing mine. Hate wasting a 100 gallons of tank space. 


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4 hours ago, Cory said:

Everyone should do this once, so they can appreciate the true value of a non scratched acrylic tank lol. It can be brutal when you have to be inside one. I've done a 180g before, you sweat so much being trapped inside working.

It is a ridiculous amount of work lol! This one was extra hard cause the top part is glued, cannot be removed, so we had to maneuver the buffer thru the 7"x20"  or so openings at the top, was reaaaaaally hard to polish the interior! 

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  • 2 weeks later...


I received my weld-on 40 acrylic cement some time ago! Ordered 2 pints of it to reinforce the seams on the bottom. The tank has some crazing on the bottom seams, and the person had this tank for a long time without using it, outside their home, so I felt reinforcing was necessary. Someone checked it and told me most likely I would be ok, but I didn't want to take chances, so here it is:

So, let's check the package of weld-on 40 first

Pretty straightforward. The kit comes in two parts, component A and B. We have to mix them in a 100:5 ratio. The kit comes pre-measured to be this ratio. But the catch is that you have only 20 minutes to work with it from the moment you mix! We have to be very careful not to waste this material, as it is costly! (a pint kit was $40).

The first kit however, I mixed all because I had to reinforce the front seam, and it was very long and had a good amount of imperfections/bubbles, so I was told I would need a very substantial amount there.

The second one though, I had to use just the amount needed to reinforce the side seams. Doing the entire pint would be a waste since the side seams are so much shorter. I had to find a way to figure out how much material I needed to make roughly a 1" thick pour (remember, amterial has a working time of 20mins only! Gotta be precise). What I did was, I took a graduated cup and poured 100ml of regular water, and then poured it on the seam, just to give me an idea of how much 100ml of weld-on would look like. It ended being too little, so I added 50 more mililiters. 150ml of water was just great for the side seam! I went ahead and dried the tank, and then re-measured 150ml of water in the cup, then transfered the water to a plastic bottle that I cut for the purpose of mixing, so I don't ruin the graduated cup.

After that I made a small mark on the bottle (red dot) so I can know when I have exactly 150ml of weld-on.

Threw the water and poured weld-on component A to the red dot (150ml).

Now I had to find a way to measure an amount of the second component (B) that would make the mixture 100:5. Luckily, the metric system made this easy! haha. Since I was using 150ml of component A I just needed 7.5ml of B to make the ratio. So, 150ml and 7.5ml.

Now I needed a guide to measure such a small amount of liquid. Well guess what? a teaspoon converted to mililiters is nearly 5! Super easy haha, So I just needed to pour 1 and a half teaspoons of component B and I was all set. Used some kitchen measuring spoons for this. Orange one is 1 Teaspoon and purple is half. So, one and one!

All ready to start mixing!

This is how I mixed it, they say to do it extremely slow in order to avoid air bubbles, but it seems it is nearly impossible to not have some. I was so worried but I was told I would be fine! (Please excuse the dogs, they're chihuahuas and will bark at pretty much a leaf blowing in the wind...)

We are using what is know as the "Tip and Pour" method, and it's just that lol! You tip the whole tank so it forms a V, with the seam you are trying to reinforce (drip the cement) at the bottom, like so:

Pouring the mixture on the seam. (Excuuuuuuse the dooooogs and the musiiiiiiiiiiic lol).

This is the front seam when I finished pouring. Notice how I made a mess? First time doing this, Should have been more careful haha. But that will be covered with substrate so ah well!

Side Seam:

Now the ugly part. This is how it looked after 1 day of curing. My heart sank, I thought to myself "oh god that doesn't look good, I screwed it up, so many bubbles". I quickly asked around and was told this was very, very common while doing this, and that I would be fine. The mixture penetrates any spaces that happened to form in the seam, and well, bubbles come out, and since the material hardens so quickly, the bubbles might get trapped. But as long as I have a firm and decent surface contact between the two panels, I should be alright! The mixture reacts and becomes extremely hot some minutes after you mix it, so that might cause a bit of crazing on the surrounding panels too, but it is harmless and nearly invisible, and frankly it is better to have a little bit of crazing than have a seam burst from stress:

3 days later of curing, everything is all hardened up, solid as rock and completely welded together! It's kinda hard to see but I welded the back panel from the inside of the sump compartment (You'll ahve to excuse the parrot this time, I know I know, I have a zoo already! xD):

Time to rinse substrate and fill it up!

After 24 hours if waiting for the water to go down from over 100`F (I live in desertic climate) to my room temperature of 79`F, it was time to put some plants! I just hope the severum, blood parrot and oscar leave them alone... one can dream lol!

Added a massive amount of cycled bio rings and seachem matrix in a net bag at the back of the sump, as well as two aquarium coop, fully cycled 20gal sponge filters, as well as an ampoule of BioDigest Prodibio bacteria culture and voila! The guys are happy in their new tank! At long last, poor oscar was tired of that 10g tank! And was outgrowing it fast! He didn't even sulk after the tank change, started swimming all around right away!

Temperature on the heater is 80 or so,a bit warm, but they're fine, properly temp. acclimated them, and the temperature will be 78-79 by tomorrow morning.

The three fellas are getting along so well! I can't believe it haha! They're even shoaling all around the tank together!

It still need some river stones, a proper cover, more plants and perhaps some driftwood, but the hard work is finally over! Been working on this tank since April or so, and now they finally have their forever home, I'm happy and they're happy! Looking forward to watch these guys grow into big monsters!

I shall update even more when I have more scaping! Thank you so much for reading!

Edited by HenryC
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