How to Cut down a Glass Aquarium

[ddelozier]

Chapter 1 of 2

How To Cut Down A Glass Aquarium
First let me state a few things. The descriptions include methods/tools I used, and the results I received. Just because something worked/didn’t work for me does NOT mean that you will get the same results. It does mean that this result is possible. Don’t go slamming me with correction Emails and PM’s. Also know: This is TIME CONSUMING and LAYBOR INTENSIVE! DIY for this project will save money, but it will cost time. If you’re short on time, patience or are not trustworthy around sharp edges, buy a prefab tank. I can promise a prefab tank is cheaper than an ER visit!

In the process of compiling the info presented here, I cut down a 65g brick tank, drilled with an overflow, and the frame was not one piece. Tank dimensions 36Lx18Dx24T. I cut it down to 12” tall. Each side had its own section of frame. The glass was 3/8” thick. The other tank cut down was a 90g tank, single piece frames, without overflow. The glass was also 3/8” think and the bottom pane of glass was clearly marked Tempered. Dimensions: 48Lx18Dx22T. I cut it down to 11 tall.

Tools: Break-blade razor(get a good one, Cheap ones break)
Spare break-blade Razor refills
Flat razor scraper (get a good one)
100 pack of spare razors (yes, you read that right)
Steel wool – Coarse works best
Denatured Alcohol(solvent to soften the silicone) – Paint thinner section at Lowes.
Glass cutter(Don’t go cheap on this either)
Large carpenters square(at least as long as the longest cut )
Vegetable Oil(we’ll get there)
Eye protection
Gloves – thick leather
Wet-dry sandpaper – 80 grit – Autozone 8 bucks a pack
Sanding block – a 4” piece of 2x4 works well if you don’t have one
Masking tape
Strap/duck tape
Electrical tape(cheap stuff)
Furniture clamps x 8
1” by 2 or 4” wood, cut at least the height of the cut down aquarium (8 required)
1”x1” Cut precisely(2-4 the width of the tank between panes(measure while disassembling, without frames) and 2 the Length of the Tank(again, measure between panes before disassembling)
1”x1”(2x4 work too), cut 8” Wider than the finished tank, front to back(3 required)
Several small blocks of 2x4(only needed as spacers, so length is not important(mine were 4”)
Sharp chizle/narrow screw driver
Silicone
Calking gun
Paper Towels(2 rolls at least)
CHEAP wide measuring tape(this will be ruined during this process, so don’t spend a lot)
Aquarium without Tempered glass sides(included for reasons that may or may not be obvious)

Steps: Remove Tank Frame, top and bottom
Clean all panes to be cut thoroughly inside and out
Clean frames
Cut glass
Sand edges
Tape tank back together
Tape off seams inside
Seal tank
Leak test


Removal of the tank frame requires a lot of time, caution and quite a bit of patience. Most tank frames are siliconed in place between the glass on all edges. This process can take a while, so don’t plan to have it done in 30 min. Using the Break-blade razor, slide under and behind all the frame/glass contact surfaces to cut the silicone. Apply a slight pressure away from the glass(ie UP) so you can see if you’re loose yet. Some tanks have a slight inside lip which makes getting underneath inside impossible. IF that’s the case, cut as much of the outside silicone as possible, then using a board and rubber mallet, knock the frame up a little at a time, going around many times. Don’t be gentle, but be sure you are applying all the pressure against the frame and not the glass. This will separate the frame, but only after the silicone along the sides has been cut.

Now we take the glass apart. Using a break-blade razor, I first went and cut as much of the visible silicone out of each of the corners as possible. To separate the panes I tried multiple methods, and I can tell you that getting to the silicone seals between two panes of glass, ie corners, is a challenge. I tried strait razors, the break-blade razors, and both were too thick on the 2 aquariums I was doing for this project. What I finally found that worked is a measuring tape. A 1” wide measuring tape is thin enough, sharp enough, and rigid enough to literally push down between the panes without putting too much pressure. Its likely that the measuring tape will get bent/torn once or twice during this process, so gloves and a cheap measuring tape are essential. With break-blade razors I could get the cut started at the top, but it would get stuck at about 6” down. If this happens, be very very gentle removing it. I wiggled it to try and get it unstuck and it caused a clamshell. I started with the Front pane of glass because it already had a couple chips.

Clean the glass thoroughly inside and out. Glass over ¼” is tough to cut, and scoring on both sides may be required. The cleaner the glass, the better the chances the cut will be clean. Now we get to the edges, where the old silicone was. Using strait razors, with a scraper, remove as much silicone as possible. Change blades often. In my experience, a razor becomes too dull to get very close after about 12” of edge. Once that’s done, using steel wool, go back along the edges to get the remaining silicone off. I know some are screaming at me(NOOOO! Steel wool will scratch the glass!!!) Short answer, No it wont. Glass is harder than steel. And even if it did pick up a particle of dust/sand and make a scratch, these will be under silicone anyways. I kept the edges wet with alcohol during this to make it easy to see areas that needed attention(denatured alcohol will both soften the silicone, and bead away from it) Get all the silicone off. Take time and get this right. If there is any silicone left, the glass may not break strait and the new silicone used to seal the tank will not seal correctly.

While cleaning the Glass, remember to clean all the silicone off the frames. Using a razor and or sharp flat screw driver and steel wool, get the frame good and clean.

Glass cutting time! If you don’t know how to cut glass, if you have NEVER cut glass(ME), or if you are cutting glass thicker than ¼”, I seriously advise contacting a local glass company and get the job done for you. Most places will charge $10-$20 per cut. This is a good safe solution. A friend at work did it for me for the price of lunch. If you’re cutting the glass yourself, do use a quality cutter, a good carpenters square, and vegetable oil to lube the cutting wheel(veg oil is not toxic and is easy to remove after cutting with soap and water)

 

[ddelozier]

Chapter 2 of 2

Sand the edges. Use wet/dry sandpaper, keep it wet and wear safety glasses and gloves. Use the sandpaper wrapped around a block. DO NOT try this by hand. Cut glass can be sharper than any razor, I’ve got a nice scar to prove it! Using a sanding block with wet sandpaper, go along the edges at a 45 degree angle, and move across the edge, do not follow it. If you run along the edge, you will ruin your sandpaper and waste time. This is not tough, and doesn’t take long. 4-5 strokes are all that’s needed. The point is to take that sharp edge off. (Glass companies will often bevel the edges for a few bucks). DO NOT NOT NOT attempt to use any form of power sander. The rapid oscillation will create heat and fracture the glass.

OK, time to start putting it back together. This should be done on a rigid, flat level surface. Seal the bottom pane into the bottom frame. This can be done with full silicone seal all the way around, or with a few strategically placed globs of silicone in the corners, and evenly spaced throughout. Make sure all the silicone stays UNDER this pane. Any above should be wiped off immediately with paper towels. This is merely to attach the frame to the bottom of the aquarium, nothing more. Once this is done, tape the vertical frames together on top of the bottom frame(no silicone yet.) Do this while the silicone is still fresh. The weight will force the pane down level and flat. This part may require a 2nd set of hands. Be sure the glass has been sanded, and still wear gloves.

TIME TO SEAL. This part gets most people in trouble, and is the crucial point at which your project can:
A) end up as a frag tank because the seals are ugly and sloppy.
B) End up as a Terrarium because it doesn’t hold water.
C) End up as a Beautiful show piece you’d proudly display.

Which end you get depends on how detailed you decide to be. If you follow the method provided, the result should be show quality. If you’re making a Frag tank and don’t care about ugly seals so long as its water tight, some of the following steps can be skipped. Please note this is Time Sensitive once the silicone is applied, so do set aside plenty of time. If you rush, you’ll either end up with a frag tank or Terrarium.

Start off with the vertical panes taped in place on TOP of the bottom frame. Using masking tape and tape along each seam. Leave 1/4”-3/8” (depending on your preference) of bare glass on each side of the seam. At the bottom of the vertical seam, cut the tape the same gap above the bottom pane to leave room for the bottom seam. Since we’re sealing all the seams, these cannot overlap.
1) Tape a box onto the bottom pane with your chosen gap away from all the walls.
2) Tape 3 sides of the box, on all the side panes with your chosen gap.
a. Be sure to account for the panes which will be inside (ie in most glass aquariums, these are the sides).
b. Leave room along the bottom for the bottom seals.
The goal here is to leave room for the silicone and make the seams strait, even, and neat.
(NOTE) For those making frag tanks who aren’t OCD, the above instructions are optional)

Once taping is done, the Sealing can begin. This will probably require a second person, so do have a volunteer/victim on hand. This has to be done quickly, so have all the silicone and alcohol you need on hand(no I don’t mean beer…that’s for after). A small cup of alcohol(rubbing or denatured works) should be close when handling silicone. It keeps the silicone from sticking to fingers. Leave 3 sides of the tank taped together remove tape only on one pane at a time. I started with the sides because they would be inside between front and back. Remove the pane and run a thin bead of silicone along the space where this pane will SIT on the bottom. Place the pane back in and push down gently. There should be a small amount that squeezes out inside. If not, remove the pane and apply more. Tape the pane back in place. Do the same to the opposite pane of glass. Don’t touch the silicone inside yet, even with alcohol. Remove the front or back pane. This one is trickier. The silicone has to be applied not only along the bottom, but along the edges of the side panes. Once the bead is in, drop/push the pane back into place and tape. Repeat for the opposite side. This should leave us with the bottom and vertical seals between panes of glass in place. Now, very quickly before the excess inside begins to set, Apply as much as needed to completely fill the gaps left by the tape. START WITH THE BOTTOM(for a reason). Go around the bottom, then do vertical corners. As you’re doing this(if possible) your partner should be following behind you with alcohol dipped fingers and wads of paper towel, to Smooth the beads into the concave shape we all know and love. If you have no help that can do this, do all the silicone application then start smoothing. Silicone has about 15 min before it begins to form a skin(ie sets up). Smooth the seams down with alcohol on your fingers. If you wish, you can use a piece of cardboard, wood or a grout tool to get the corners neat. I used fingers, but this was destined to be a frag tank anyways. Make sure during the smoothing to remove as much extra silicone as possible from the taped areas. Once the corners are smoothed, peel off and remove the tape. If the tank is designed for an Overflow, this should be cut down before hand, and installed last. Additional taping may be required, plan ahead.

Once all the seems are smoothed, run a bead of silicone into the top frame and set it in place. Remove excess silicone inside/outside. NOW we come to the boards/clamps portion. Place the spacer pieces inside away from the seams. Then take the boards cut to precise length of the inside dimensions, and gently force them into place near the bottom(on top of the spacers as not to touch the seams. The idea is to force the bottom of the panes back into the exact dimensions they should have been. If you taped correctly, and the cuts were clean/precise, this should take very little if any pressure. Then take the boards cut to the height of the finished aquarium and place them outside against the top and bottom frame. Using clamps, force the top of the glass against the frame by clamping the glass and the board outside the frame. Do this every 18” across all sides(short sides may only require 1).
Last but not least, take the 3 boards cut wider than the tank front to back and lay them across the tank between clamps. Some sort of weight is needed. I used a tote of dry rock(30ish lbs on a cut down 90g). The idea is to press the frames, top and bottom together. All this is optional and may NOT be required, but I did it to make sure things were square.

Let the tank sit like this for 24hours. Using a razor and glass cleaner, clean the tank well of any drips or slops in the silicone. Rinse it well and fill it with FW for a water test. Let it sit slightly elevated ie on boards, blocks or stand with water in it for 24-48 hours. Provided no seams leak(resulting in either a tear down and redo, or selling as a Terrarium) the tank is ready to be used.

Last but not least, the Disclaimer: The methods described in this document were used on the project described. Your results will depend not only on your care and skill, but on other factors in your own project, such as glass thickness, silicone seam thickness etc. The info presented here is meant as a first hand account, and point of reference for you to start with in devising your own plan. The total time start to finish of both tanks was about 18hours. If you chose to attempt this sort of project, be ready to try multiple different methods until you find one that works. If you chose to use the suggestions provided, I take no responsibility whatsoever as to the outcome you get. I did this as a last resort to save a couple of tanks that were destined for the garbage. I documented it because I could find very little in the way of reference material for cutting down a glass tank. The most common advice I found on this subject was (DON’T DO IT. Sell the tank and buy one the size you need). Where’s the fun in that?

GOOD LUCK!

PS...except for cutting, these are also the same steps needed to totally cut apart and reseal any glass aquarium. I've done quite a few. I always watch Craigslist.org for Leaky tanks...they're cheap and easy to fix if the glass isnt cracked.

 

[nanoreefing4fun]

WoW - Well documented, really enjoyed the read, thanks for taking the time to make the great write up and share with our RS family !

This is some Serious DIY

Would love to see some pics

I can see where you can get some real deals on leaky craigs list tanks

 

[DaveK]

That's a couple of great posts. I don't think I'd go to that much trouble myself as this is a tremendous amount of work, but sometimes that's yhe only way you can get a tank the exact size you need.

 

[jpond210]

I was just searching for this the other day. Great thread. I want to cut down 50g.

 

[ddelozier]

This is one of the tanks I cut down. Up and salty. Cycling at the moment


Sent from my iPhone using misspelled wrods!