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DIY Styrofoam/Drylok Aquarium Shale Wall Background

76K views 142 replies 11 participants last post by  Deeda 
#1 ·
Hi Everyone.

I've been working on a background for about a year and a half, and should be ready to install it in my tank soon. This background will be for a 75 gallon US Native stream/river tank, and I wanted to try and build a biotope that you might find in one of our local rivers, all of which have shale formations along the river bank. I also wanted to create something that I haven't seen before, so my intent was to have the faux slate stratification at a downward angle. Since much of my research came from this forum, and many of your paved the way for guys like me, I figured that it was time to give something back and show you not only what you've taught me, but what I figured out on my own as well, and we can finish this project together.

The background was carved out of styrofoam boards, then each glued at a 45 degree angle or so when they were done carving. I measured as I built it up. the gap behind the foam board and base were filled with spray foam and river rocks (to reduce buoyancy). I used Gorilla Glue to bond the styrofoam boards together and also used plastic popsicle sticks to help stabilize and bond them. On the left side, there is a PVC pipe that goes down into the background with an intake that I made for the intake tube of my canister filter. There is a removable section of carved foam covering it that allows me access to clean and clear the intake of debris. The part that sticks out of the left side hides the intake.

The pics and video below show what the background looks like today. In the subsequent posts, I'll show how I constructed it. Hope you all enjoy it and thank you for all of the posts of your backgrounds that helped me!

View from the left side:


View from the right side:


Video:


The paint is the second coat of Drylok, tinted to resemble the base rock color of our river cliffs. The first coat was just Drylok gray. I will be stippling lighter shades of this color a few times to make the rock less monotone and more realistic, and then finish with light color highlights. Construction steps to follow in the next posts. It may take me a few days to get this thread going to the point we are today. But, I'll start with my first steps.
 
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#2 ·
I started by building a foam board frame, then started cutting my soon to be faux shale layers. I carved each one, then glued them one at a time. I started by working on the right of three sections. Then, as I went a long, I started on the second section to coordinate the seam between the two. I wanted the seam to look like a natural looking crevice in the rock rather than just a seam in a background. Eventually, I did the same thing with the third section, and built it up one layer at a time for each section.

Starting frame of the right section with some of the layers carved and glued, you can see the popsicle sticks that were eventually glued in as well for more support:


Wood kabob skewers came in handy to position my work as I went. Eventually, the right side of the frame was discarded and the layers now go right up to the glass.

Working on the right and middle sections, matching the crevices created to cover the seam:



Flat foam board surfaces don't look real. When using this concrete block to weigh down the glued boards, I learned that was a good way to make them look realistic, by pressing things into the foam board and breaking up that flat surface:



Building up the right and middle sections:
 
#3 ·
The wooden kabob skewers also came in handy to carve out cracks in the foam, to look like rock cracks:



In this picture, you can see as I built up one layer at a time, I used spare foam board pieces as a support to arrange and glue my carved boards. This was needed to support the weight that I put onto the glued boards. You can also see how I used the plastic popsicle sticks and glued them into drilled holes in the foam board for added support and structure:


 
#4 ·
Pressing things into the foam board surface, as I said before, makes the rock more realistic. I also started incorporating pressing objects in to look like Devonian sea fossils. Coral pieces, sea shells, and even a simple spring, that I could bend, did the trick:




It started to look a bit like real shale fossil rock... Here is a pic showing my work along with the photo that I used as my inspiration to carve:
 
#5 ·
Showing the work on the third section:




I used spray foam and stuffed river rocks into the gaps behind the background base that would be glued to the glass and the carved out faux shale foam boards. Make sure that you use rubber or latex gloves to protect your skin from the foam...nasty stuff. By the way, the spray foam also helps to really bond the foam boards too:


After spraying, I had to carve away the excess, and make sure that the two sections fit. Eventually, I did this between the second and third sections as well:
 
#6 ·
The next step was to build the cannister filter intake and the right end to finish off the background structure:




And now to hide the intake pipes... I painted the PVC pipe black with spray paint, then built some foam structure for my final faux shale layering of the left side, third section:

 
#7 ·
This piece is removable so that I can access the drain pipe for cleaning and clearing debris. The challenge for this was to design a way to hold it in place and have it not float away. I won't know if it finally works until I install the background and fill the tank with water, but I think that my design should work. If it doesn't, then I'll redesign and adapt.


The drain is now hidden, in the hole in the faux rock:




The removable piece is held in place by the layers above it, as it slides into the structure for a tight fit:
 
#8 ·
Here the structure is fitted into the tank. It is a tight fit and will be a challenge to glue it in. I'll explain how I did that after I'm done...not quite there yet.



I had a gap in the back because not all foam boards are square or equal. So, I used egg crate and spray foam to give me a good place to glue the left and third structure to the glass, giving me a good cosmetic fit on the outside. The other two sections butt right up against the glass just fine. I also used spray foam to level out the third/left section on the bottom for the same reason:


this pic shows the structure from the left side of the intake pipe:
 
#9 ·
To keep the bottom of the removable piece from floating up and away, I glued in some plastic spaces that I found at the hardware store in place into the structure, and also into a foam piece glued to the underside of the removable piece. I can slide a plastic popsicle stick into the hole through both plastic spacers to hold it in place. I think it will work...time will tell.

The spacer glued into the structure


..and into the removable piece:


The plastic popsicle stick fits right in, holding it in place:
 
#10 ·
Last week I painted the first layer of gray Drylok to cover the entire structure other than where I'll silicone it to the glass. I wanted to hide all things pink and yellow...


Middle section:


Left section:


Left section without the removable piece:
 
#11 ·
And to bring us up to date, this past weekend I painted the base color. I used gray Drylok, mixed in charcoal color liquid cement dye, and a little bit of yellow paint to make it less gray. This turned out to be the right color mix for the rocks that I'm imitating in my river:


I used several paint brush types to get the paint mix into every crack and crevice, this time to hide the undercoat of Drylok gray:


As the background sits today:


Here is a video showing in detail how I carved the shale pattern for each foam board, and how I made the cracks too:


I started this process a year and a half ago. I lost time in the build due to family matters and other things (like my outdoor hobbies), and also to think things through on how to do this. There were time gaps where I struggled on a road block in my process before I came up with an idea how to proceed. And there were times were I wasn't motivated...but, now I'm so close to finishing that it should be long. It's time to get this tank done and cycled, and get some fish in it.

I think that if I was diligent from day one, that I could have worked on this an hour or two a few times each week, that I could have gotten to this point in a month or two. Well, I hope you like it so far. I'll post updates as I finish this build. Next up, stippling layers of lighter shades of the base rock color and then highlights. After that, gluing/installing this background into the tank. It fights tightly between the bottom of the tank and the tank frame/top, but I still plan on using a lot of silicone to keep this thing from floating up. I may wind up finding a way to brace it in at the bottom. I'll cross that bridge when I get to it I guess.
 
#12 ·
Sorry folks, I messed up and duplicated a pic in a post above, it should have read like this:

Chasmodes said:
I started by building a foam board frame, then started cutting my soon to be faux shale layers. I carved each one, then glued them one at a time. I started by working on the right of three sections. Then, as I went a long, I started on the second section to coordinate the seam between the two. I wanted the seam to look like a natural looking crevice in the rock rather than just a seam in a background. Eventually, I did the same thing with the third section, and built it up one layer at a time for each section.

Starting frame of the right section with some of the layers carved and glued, you can see the popsicle sticks that were eventually glued in as well for more support:


Wood kabob skewers came in handy to position my work as I went. Eventually, the right side of the frame was discarded and the layers now go right up to the glass.

Working on the right and middle sections, matching the crevices created to cover the seam:



Flat foam board surfaces don't look real. When using this concrete block to weigh down the glued boards, I learned that was a good way to make them look realistic, by pressing things into the foam board and breaking up that flat surface:



Building up the right and middle sections:
 
#14 ·
Thank you Deeda!

I added another coat of Drylok paint today, the same basic charcoal color with a splash of yellow, but a little bit lighter shade. This is to enhance the cracks and bring out the rock into a 3 dimensional appearance rather than a monotone dark charcoal color. I will do this a few more times, but with a lighter shade and less paint each time. One of these coats will have a more brown tint. After that, it will be brighter colors for highlighting only, but maybe some very light red and/or green added to break up the gray. I will decide as I go based on what it looks like.

This coat was applied by stippling the paint onto the background with a sponge. The key was to not use too much paint, and try and keep the sponge somewhat dry. Also, this coat covers more surface area than future coats. The mix was Drylok gray, a dab of charcoal cement dye, and some yellow acrylic paint:


After testing on a scrap piece, I moved to the real thing and applied the paint to one section to make sure:


I was pleased with the result, so I stippled the entire background. All three sections completed, view from the left side:


View from the right side:
 
#17 ·
freshwaterhobby said:
Super creative and really cool looking!!
I didn't know all those materials were safe for aquariums...but I assume they are since you have put so much heart and soul (and time) into it :)
Thank you freshwaterhobby! Yes, they're safe. I did a ton of research before moving forward with this on this and other forums. Basically, once dried, all of the materials used are inert. Drylok is a waterproofing sealant and is also inert. The only thing that you have to be careful with when buying Drylok is to make sure that you get the regular Drylok paint, and not the Drylok Extreme, because it does have chemicals to prevent and kill mold, which could be harmful to your fish.
 
#20 ·
I painted the last lighter layer of this paint mix. I'm really happy with it so far. It is still a monotone color, although it no longer is the charcoal color of the cement dye, the yellow gives it a greenish gray tint. So for the next layer or two, I plan to add a little brown and maybe green. I don't think that I'll cover the entire wall though, just a dab here and there. I may even focus on a few of the shale layers to add to differentiate some strata, as you might see in nature:




I really like how using Drylok rather than a layer of dried cement allows you to bring out the detail that you carve. That is a good thing unless you carve a mistake! In this case, the faux fossils that I pressed into the foam show up well. I'm happy that i started with the darkest color first and then added the highlighting, because it really makes the cracks and faux fossils pop.



I used springs that I had laying around the house to imitate crinoid stem fossils by bending them and pressing them into the foam. I also pressed in small sea shells to imitate brachiopods and other bivalves. The coral that I pressed into the foam turned out nice too. It is subtle, but was enough to break up the flat shiny surface of new foam board. I don't know how much will show up later after algae builds up, but for now, I'm happy with how it turned out so far.
 
#22 ·
One of my biggest concerns with the background is the amount of foam that I used and the risk that the entire thing will float up to the top after I fill the tank with water. To mitigate those risks, I filled the structure with river rocks and used spray foam to fill in the gaps. The foam will help bind all of the foam boards together along with the glue and plastic popsicle sticks that I used for the internal structure. The river rocks were to offset the buoyancy that the extra foam might cause. Also, the structure is big enough that it fits tightly in place under the frame of the tank. The junctions of the three foam sections also are shaped in such a way as you can't just pull them straight out. I plan to use a ton of silicone to affix this background to the tank glass underneath, on the sides and on the back of the background structure. The Drylok application made the fit even tighter. It fits so tightly that I can't pull it straight out to the front of the tank. I think that it might not need the silicone to stay in place, but I'm not going to take a chance on not using the silicone.

Last night, I fit the structure into the tank. The tight fit discussed above created another problem. Not only will it be challenging to apply the silicone neatly, but I had to really push to get it into place. The tight squeeze caused about a quarter sized spot of Drylok to chip away at the junction of the center and right sections. I'm going to pull it out and repaint that spot, but if it happens in during the final installation, then I'll just have to do an in-tank touch up. I'd rather not do that, but....I gotta get it done.

Here's what it looks like from the left side, you can't see the spot that chipped away. The spots that you see are just a reflection off of the glass.

You can see where the paint chipped away near the top of the junction of the middle and right sections, leaving the pink foam exposed. It should be easy to fix, so I'm not that worried about it.
 
#23 ·
I installed my background into the tank last night with silicone. I faced several issues that I had to deal with that have bothered me since I finished the construction of this beast, and two issues that I hadn't thought about. The issues were:

1) I used enough foam board and spray foam when constructing this background to float my boat, and needed to use a ton of silicone to keep it from ripping away and floating.
2) Because this background fits tightly when fitted into the tank, you have to slide the last section in to get everything to fit, so, I couldn't silicone one section at a time in place. I needed the silicone to remain uncured and wet during the process.
3) How exactly could I accomplish physically solving the two problems above without making a mess.
4) While applying the silicone, I wasn't sure if I purchased enough tubes, and it was Thanksgiving afternoon, and finding a store that was open to sell them to me was a problem. Not only that, we had family plans, and time for me to work was limited.
5) The silicone fumes were intense.

Below are pics of the process, and explanations on how I dealt with each issue.

First, I cleaned the tank and drew lines with a sharpie of approximately where I needed to apply silicone directly to the glass.


Issue #1: Applying enough silicone to keep it from breaking away and floating. I applied silicone directly to the glass, then to the back and bottom of each background section. I cut each tube to allow me to apply a thick bead of silicone to each surface. On the backgrounds, I focused on areas that may not make contact with the glass, thinking that the silicone on the glass and in a given crevice would make contact and bond, and the areas that made direct contact with the glass would have sufficient silicone from the amount that I applied to the glass.





Issue #2: Solved by installing everything as soon as possible. My only mistake was applying silicone to the right side of the last section. I should have applied a thicker amount of silicone directly to the glass, so that when I slid the last section into place, it wouldn't make a mess. Issue #3: I left enough room on the edges of the structure to be able to lift and maneuver each section into place. This also kept most of the silicone out of sight.


Issue #4: Solved, because I barely purchased enough. I went through 7 tubes. Using a very thick bead causes you to go through each tube much quicker than you would for household applications. Issue #5: My entire rec room still smells of silicone. I had a really tough time after installing the first section, especially reaching over the tank. The fumes were intense. I had to turn away, take a deep breath of fresh air, then hold my breath while working in the tank the rest of the time. I opened the door to the outside, and that, at least, allowed me access to some fresh air. It didn't help inside the tank though.

In the above pic, you can see the mess that I created while sliding in the last section of the background. It's not a big deal. I'll take a razor blade to it after it cures. Here's a closer look of the mess:


After gluing it all in place, and pressing it as firmly as possible against the glass, I installed the removable piece for a pic of what is should look like once the tank is up and running:


Next steps:

I need to paint the glass on the sides and back where the background meets the glass, to hide the ugly silicone work. There is a gap between the first two sections where light passes through. Painting the back of the tank should hide that and make it look like a natural crevice. There is a gap on the lower part of the left side that I may have to deal with. I haven't decided if I'll apply a little foam there and carve it back, and paint it, or just leave it as it is. It bothers me though (you can't see it in this pic), because the silicone shows through there and looks unnatural.

I'm going to give this some time, about three weeks, to completely cure. Then, I'll fill the tank and test to see if the installation and glue holds up enough to move forward. I'll leave it filled for 24 hours. If it doesn't rip away and break the glass, and flood my basement, then, I'll move ahead. I am fairly confident that it will be OK.

I will begin working on the fake roots. I trashed what I had done so far...didn't like it. I have a plan though. In the meantime, I need to head to the river and start collecting rocks, gravel, and sand to hardscape the tank and get it ready to set up. Once I do that, then I'll set the tank up. The roots will be installed after the tank is up and running, unless I can finish them earlier than planned.

As far as substrate goes, I would like to grow stargrass at the right third of the tank, so my bottom layer of substrate will be dirt to provide nutrients for the grasses. Sand and gravel will go over top of that.

The thought of installing this thing posed some issues and was a source of my procrastination...the thought that it wouldn't work had occurred to me. Yesterday, I woke up determined to move forward. I'm glad that part is behind me and my stress level is way reduced.

After the tank is cycled, then the fun part begins...collecting and stocking.
 
#25 ·
skwerl said:
Thank you so much for sharing this process with us! It is looking great so far!
Thank you skwerl, and for following along!

Next steps while the silicone is curing (I'm giving it 3 weeks, just to be safe, and it still smells like vinegar):

-build the DIY sycamore roots. I'm scrapping what I've done so far on that - don't like it. I'm going to try some new things, using PVC pipe, plaster gauze wrap, grout, Drylok and cement dye to form the roots. Why not just collect driftwood? Because, I want them to be a certain shape and form to hide my powerhead and equipment, and to have them easily removable for maintenance.
-collect sand and river rocks

-Hopefully Santa will bring me a new light fixture. My old fluorescent fixtures aren't functioning, and the cost of parts is probably worth more than the fixtures. I have my eyes in a Finnex planted light. This is the only equipment needed.

When setting up the tank, the right side of the tank will have substrate to support growing river stargrass. After filling the tank and setting it up, I'll collect fish and stock the tank. I'll eventually collect the grass to plant (next summer).

So, things will move along quickly in a few weeks. I am chomping at the bit to get this tank set up!
 
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