Ratherbeflyen
Well-Known Member
My 72" x 24" x 30" tall 220 gallon tank is about to turn 3 years old and I've decided to this experiment has gone on long enough to share it. I covered the back wall of my tank with a 3D background made from sheets of lighting diffuser, black sanded grout, and lava rocks. I built the background outside the tank, let it cure, and then used aquarium safe silicone to adhere the background to the glass.
A disclaimer here. I've never seen anyone else use this method of either colored sanded grout or black lava rock reef. I've read a lot of people advising against it. This is my second tank using this method, and I've grown fish and coral in both. After 3 years I've never had a problem with iron, aluminum, silica, toxins etc. that I was told would make this impossible.
I like having the back wall covered. Partly because I hate scraping/cleaning the back wall, but also because putting everything right on the back wall gives the tank a greater sense of depth. It provides unmatched empty space for swimming room and tank maintenance. You also don't have to worry about rock structure falling risking your coral or breaking your tank. It does make changing your rock work more of a challenge. I have 5 rocks laying on the sand that I can move total. The other added bonus is there is no where that detritus can settle and build up. I can reach every inch of my sand with a gravel vac when I do water changes.
For the construction of my background I started by making a wood box that matched the inside dimensions of my tank, including the overflow. This gave me a place that I could experiment with the layout without scratching or breaking the tank.
Grout is designed to stick to rocks, so you can use any rock you want. You can probably even use wood or plastic if you wanted to. I used black lava rocks I picked up from a local landscape supply company for $0.17 per pound. You may choose to use a more aquarium safe rock or just about anything else you want. You could add wood or plastic and make a fantastic terrarium for frogs, snakes, turtles, etc too.
Once the layout was decided, I used lighting diffuser and black sanded grout to actually build the background. No foam or zip ties, it's just held together like brick or stone mortar. It is made into 5 separate pieces to be able to install in the tank around the center brace. 3 back pieces, 1 side, and the overflow cover. It also gets pretty heavy and I wouldn't want to muscle around 200+ pounds of this background. You can break it up into as many pieces as you want. My only advice is to avoid making straight vertical or lateral lines. Jagged and angled edges become seamless once installed. If you do see a seam or any thing else you don't like in the background, you can glue more rocks to the background once it's installed. I glued in a dozen or so small rocks later to smooth the transitions between the pieces.
The large rock in the right corner was molded in place, but is not part of the background. It comes out separately as it was too heavy otherwise.
I let it dry for a couple of days, then broke it down and moved into water to cure. This is a very important step. Grout is a cement product and cement is very caustic. Just like all DIY rocks made from concrete products, it will drop the PH as well as leach out some lime and color dye making a mess in your tank. I made a 2x4 frame and lined it with some plastic. Then to change the water, I just unscrewed one of the boards and let the water out then refilled it with tap water from the hose. I repeated the process many times over 3 months.
Once it was fully cured, It was installed in the tank. I covered all the front and side glass with foam insulation, wood, or lighting diffuser. The pieces are heavy and awkward. It's almost a certainty that you'll bump a corner somewhere and scratch or break the tank. So it's just easier to cover it. Then it's just several tubes of silicone and some bracing for a day.
Next month is going to my 3 year anniversary of setting up this tank. I really like it and the background functions well as my only source of live rock. My only filtration is an old precision marine venturi skimmer, algae scrubber, and refugium. I have never used any of the nitrate and phosphate removal products or chemicals.
The only thing I would have done different was the cave. I like the way it looked when the tank was new, but now that the coral has taken off I would rather have more space to add more coral. My tank has a 24" center brace that makes access to the middle difficult and touching the back corner of the tank impossible with your hands. So the glass in back of the cave was hard to clean in the beginning and now all the coral makes it almost impossible to get a scraper in there without breaking off a couple of branches of coral. I might do the cave rock structure again, but would not leave any bare glass on the back of the tank.
A disclaimer here. I've never seen anyone else use this method of either colored sanded grout or black lava rock reef. I've read a lot of people advising against it. This is my second tank using this method, and I've grown fish and coral in both. After 3 years I've never had a problem with iron, aluminum, silica, toxins etc. that I was told would make this impossible.
I like having the back wall covered. Partly because I hate scraping/cleaning the back wall, but also because putting everything right on the back wall gives the tank a greater sense of depth. It provides unmatched empty space for swimming room and tank maintenance. You also don't have to worry about rock structure falling risking your coral or breaking your tank. It does make changing your rock work more of a challenge. I have 5 rocks laying on the sand that I can move total. The other added bonus is there is no where that detritus can settle and build up. I can reach every inch of my sand with a gravel vac when I do water changes.
For the construction of my background I started by making a wood box that matched the inside dimensions of my tank, including the overflow. This gave me a place that I could experiment with the layout without scratching or breaking the tank.
Grout is designed to stick to rocks, so you can use any rock you want. You can probably even use wood or plastic if you wanted to. I used black lava rocks I picked up from a local landscape supply company for $0.17 per pound. You may choose to use a more aquarium safe rock or just about anything else you want. You could add wood or plastic and make a fantastic terrarium for frogs, snakes, turtles, etc too.
Once the layout was decided, I used lighting diffuser and black sanded grout to actually build the background. No foam or zip ties, it's just held together like brick or stone mortar. It is made into 5 separate pieces to be able to install in the tank around the center brace. 3 back pieces, 1 side, and the overflow cover. It also gets pretty heavy and I wouldn't want to muscle around 200+ pounds of this background. You can break it up into as many pieces as you want. My only advice is to avoid making straight vertical or lateral lines. Jagged and angled edges become seamless once installed. If you do see a seam or any thing else you don't like in the background, you can glue more rocks to the background once it's installed. I glued in a dozen or so small rocks later to smooth the transitions between the pieces.
The large rock in the right corner was molded in place, but is not part of the background. It comes out separately as it was too heavy otherwise.
I let it dry for a couple of days, then broke it down and moved into water to cure. This is a very important step. Grout is a cement product and cement is very caustic. Just like all DIY rocks made from concrete products, it will drop the PH as well as leach out some lime and color dye making a mess in your tank. I made a 2x4 frame and lined it with some plastic. Then to change the water, I just unscrewed one of the boards and let the water out then refilled it with tap water from the hose. I repeated the process many times over 3 months.
Once it was fully cured, It was installed in the tank. I covered all the front and side glass with foam insulation, wood, or lighting diffuser. The pieces are heavy and awkward. It's almost a certainty that you'll bump a corner somewhere and scratch or break the tank. So it's just easier to cover it. Then it's just several tubes of silicone and some bracing for a day.
Next month is going to my 3 year anniversary of setting up this tank. I really like it and the background functions well as my only source of live rock. My only filtration is an old precision marine venturi skimmer, algae scrubber, and refugium. I have never used any of the nitrate and phosphate removal products or chemicals.
The only thing I would have done different was the cave. I like the way it looked when the tank was new, but now that the coral has taken off I would rather have more space to add more coral. My tank has a 24" center brace that makes access to the middle difficult and touching the back corner of the tank impossible with your hands. So the glass in back of the cave was hard to clean in the beginning and now all the coral makes it almost impossible to get a scraper in there without breaking off a couple of branches of coral. I might do the cave rock structure again, but would not leave any bare glass on the back of the tank.
