River Aquarium With Custom Concrete 3D Background




Intro: River Aquarium With Custom Concrete 3D Background

This is a combination project, both the "river tank" setup and concrete background can be implemented individually or combined in any aquarium of any size.

Where to begin?.... How about a made up FAQ...

What is a "river tank"?

A river tank is a specialized aquarium or "biotope" that simulates a river. Some river tanks just use different levels with various pools to create the appearance of a trickling stream, the kind I am interested in involves using a high powered pump to blast water across the tank.

Why would I want to do this?...

Ive been interested in keeping Hillstream loaches for a while. Hillstream loaches, as well as most loach specie's natural habitat are the fast moving highland rivers of Asia. While most fish can adapt well to aquarium life, a lot of species will never be healthy, they will never breed and basically live out a short and miserable existence for the fulfillment of our strange desire to replicate the underwater natural world in our living rooms. It was not until the concept of the river tank that the Hillstream loach was successfully bred by hobbyist. While breeding in an aquarium isn't a absolute sign of well being, it is a small step in the right direction.

The Hillstream Loach is a pretty amazing little fish and one of the more exotic freshwater species available. They are now being successfully bred in Asian fish farms but there are still many wild caught Loaches in the aquarium trade. They are sold along side tropical fish even though they are a cold water species. Many are bought out of excitement and most never live a very long life in a regular aquarium. Much like most "novelty" fish their uniqueness and beauty are their greatest downfall.

This is a cold water species and should this instructable peak anyone's interest enough to consider keeping these fish, please do so with caution and full awareness. There is a lot of good information available on how to keep these fish properly. They require a lot of oxygen and lots of water movement, their diet consists mainly of algae and if kept in a community aquarium it must be peaceful and non-aggressive..

What is a Custom Concrete 3D Background?

Glad you asked.... A lot of aquarium enthusiast have been creating their own unique and very realistic looking rocky aquarium backgrounds using nothing more than Styrofoam, some concrete and a bit of concrete die. For about $20-$30 you can create a pretty amazing looking aquarium that would not be possible using real rocks. Well, you could, but it would weigh several hundred pounds and there is a pretty good chance you would most likely break your aquarium. Not to mention how hard it would be to find rocks that fit so perfectly to form a rock face.

Might as well get this out of the way...

Is it safe to use concrete in an aquarium?

I'm not an expert, but people have been doing this for years with no known ill affect. After the leaching process (last step) anything that will dissolve in water is most likely removed. In my personal opinion, this is no more or less dangerous than any other type of natural rocks that have been used in aquariums.

What about Styrofoam?

Ah, the (Red) Plastic Scare... At least try to use "food safe" polyurethane. I used a salvaged Styrofoam food cooler for my project. If you're one of those anti-plastic types... There is probably nothing I can say that will convince you this is safe...You should, if possible try to use our ever growing and over abundant supply of packing Styrofoam discard rather than buying new sheets.

Which type of concrete should be used?

There are so many choices... I'm not an expert, in fact this is the first time I have ever used concrete beyond anchoring. Some people use hydrolic cement, however after learning that this type hardens in less than 3 minutes I decided that this was not nearly enough time to work with. I just went with 10lb bucket of Quikcrete quick setting repair cement. You most definitely do not want the type with any small stones, which will have to be sifted out, so refrain from buying the ultra cheap 60lb bag. The tubs are much easier to work with and will not tear or rip open like the big paper bags.

A few considerations...

If you plan to take on this project you have to either be starting with a new aquarium or you must have a separate tank to safely house your fish for up to one month.

It will sound cruel, but you might consider offering your tank a few sacrificial feeder goldfish after leaching, in order to cycle or "age" your aquarium and insure it is safe for your rare species. I plan on cycling mine with white cloud mountain minnows, which I plan on happily keeping afterwords. White Clouds are known for their hardiness and are commonly used to introduce aquatic life into new aquariums to get the aging process started...It is a fact of aquarium keeping, the cycling process does kill a lot of fishies....

Dangers to self:

You will be working with unsafe and very precariously extended razors. I managed to cut myself only once. If you're the type that gets cut just looking at something sharp.... You were warned.... Cut away ---> from face and hands.

Also, use gloves when working with cement. Unless you're a seasoned concrete Mason, your delicate, baby soft skin will be damaged pretty severely. I used latex disposables.

Step 1: Material & Tools

For the background construction:

Recycled if possible and preferably of "food grade" plastic. You can buy sheets and blocks from hobby stores.

1" paint brush:
Don't spend a lot, but don't buy the absolute cheapest. It can not be reused again for any other purpose.

A razor knife and a lot of blades:
I used the medium size snap off type. The blade can be extended all the way about 3-4 inches, which is very helpful. Styrofoam is very easy to work with but this project involves hours of cutting, trimming and slicing and the blade should be changed once it starts to make a lot of squeaky noises.

I used hot glue to create protruding rocks and cliffs. My background uses tension to keep all the pieces in place, but my aquarium is only 10 US gal. If you want to create a background in a large tank (30+ gallon) you will have to glue the pieces to your aquarium. Styrofoam is still quite buoyant even when covered in concrete. I wouldn't recommend using hot glue if this is the case... There just isn't enough time to try to glue them to the aquarium. You can use 100% silicon caulk. Make sure it cures for 48 hours and use the good stuff.

I used a 10lb tub of regular Quickcrete quick set repair cement. There are many different types of concrete and I honestly do not know which is best. Some suggest "hobby cement", some people use hydrolic cement. You can also use acrylic fortifier to aid in strengthening the concrete.

I used Quikcrete charcoal coloring to create a very dark background. You can use whichever colors you like to create your own custom background.

Mixing containers:
You will need a suitable containers to mix your concrete and pre-mix your concrete color with water. I used a small plastic tub to mix concrete and an empty rubbing alcohol bottle for the coloring. You will also need a spoon to mix and scoop concrete.

For the river:

A powerful submersible pump:

I used a 250 GPH pump, in combination with the regular 10 gallon power filter the water is turned over 25+ times per hour.

Plumbing parts:
The original river tank design has filtered intakes on one side of the tank and the outlets on the other. This is suppose to create a one way water flow. After attempting this, I found that this design wasn't appropriate for my tiny 10 gallon river.

I used a 1/2" threaded poly cut off nipple, one 3/4"x3/4"x1/2" PVC Tee and two 3/4"x 1/2" threaded elbows.

Step 2: Planning and Design

Begin by measuring your tank's dimensions. You will need to plan for accommodating or concealing aquarium equipment such as power filters, heaters and electrical cords. Keep in mind, after all is said and done, your background will be up to 1/2" or more thicker.

You should spend a considerable amount of time planning and perhaps even sketching a layout. You can get ideas by looking at scenic pictures and if you're lucky enough and live near a nice rocky river go spend some time outdoors. I have lived in the Rocky's all my life which may have been inspiration for my block / shear cliff / sharp type design... As for the black... You can probably blame Ozzy...

Decide on colors, textures, layers... Where you want your rock faces to jet out or protrude.. Do you want sharp edges or smooth and round rocks?... The great thing is that there really isn't a wrong way to do this.

Once you have a general concept you can begin by rough cutting and gluing the bulk of your background. You will probably have to do it in sections. Mine is comprised of four pieces. The lid of the cooler on the left created a large protruding wall which I added a couple blocks to. The second from left is a filler piece which accommodates the arm of the power filter. The third is a small double layered rock (top right) which wedges the fourth big rock. The fourth or right side block is the bottom corner section of the cooler. The large pump is hidden inside this rock.

Step 3: The River...

For my river tank I chose not to use the original river tank design. There simply wasn't enough room in my small 10 gallon tank. I did want to completely conceal the pump. I cut the bottom corner off the cooler to create a "rock" to house the pump. I then cut two holes for the double outlet manifold.

The double outlet manifold was built using various common plumbing and irrigation parts.

Step 4: Technique

For the most part you should carve up almost all of the surfaces of your rock wall. The technique I used was to just slice in every direction to create texture. You can create cracks or cliffs by first cutting a line about 1/2" down and then cutting in at an angle down to the first straight cut. (see pics)

Don't spend a lot of time on any small details, they will disappear later when covered in concrete. Just make it roughed up and jagged. There is no wrong way just use your imagination and have fun!

Step 5: Creating Protruding Rocks

To create dimension you can glue smaller rocks to the big pieces. Some people glue first and then cut, for me it is easier to cut the small rocks and hold them in place as I carve around them. If they are glued its much harder to cut at angles.

Step 6: Test Fit!

Its very, very important to test fit everything with your aquarium equipment in place, including the hood. Make any final adjustments and keep in mind the cement will make the final background much thicker!

Step 7: 1st Layer of Cement

Put down a good layer of newspaper or plastic sheeting to work on.

Mix a small runny batch of concrete. The first layer does not need color. You will be painting a thin base layer using your paint brush. Its messy work but concrete cleans up pretty easily.

Let this set for about 24 hours.

Step 8: 2nd and Final Layer

The second layer is where you will add the bulk of the cement. I pre-mixed just enough cement color in an empty rubbing alcohol bottle to finish the entire project. This ensured an even color throughout. The cement should be thicker than the first layer. Mix as much as you think you will use before it will get too dry. You can sprinkle a bit of water into the batch after a while if it gets too dried to use.

I used my hands to form this layer. You can get a smooth surface by working the concrete smooth or a rough surface by just quickly laying it on. This layer should be quite thick.

Allow this layer to set for another 24 hours.

The third layer is the detail work. I sharpened up the edges and made finishing touches.

I let this cure for 48 hours before test fitting.

Step 9: Leaching

In order to make this aquarium safe for fish the concrete must be leached. The process is long... On day one I filled the aquarium to the top and added a pound of salt. Th pH was off the charts! My tap is 7 but the tank water didn't come down to below nine until three water changes and one week. I left the pump running the whole time to circulate the water. I did a full water change every two - three days for 2 weeks and now the pH is steady at 7. I am currently on week 3 and will add fish in another week.

The accompanying image is from today. This is not the finished project. I will update in about a week while the tank is being cycled. I also plan on covering the back of the aquarium with black plastic to keep light from showing through the seams. Meanwhile I will be searching for matching rocks to add to the foreground. If I am unable to find any, I will just make some matching rocks out of solid concrete. I am considering black sand as a more natural looking substrate. I bought the white sand out of impatience and thought it might contrast well against the black rocks. It looks OK but I think black will look much better.

Thanks for viewing! It may not seem like it, but this project was incredibly easy and a lot of fun! My total cost for material for the background was about $15. The river equipment was about $30. I am really looking forward to the moment this thing comes to life! It may not be absolutely perfect but it is looking great and is the coolest aquarium I have ever had!

Step 10: Update 9-8-10



    • Tiny Home Contest

      Tiny Home Contest
    • Metalworking Contest

      Metalworking Contest
    • Furniture Contest 2018

      Furniture Contest 2018

    21 Discussions


    3 years ago on Step 8

    I could see preparing a small batch of colored cement to paint portions for effect. Paint the crack darker add the illusion of texture. I am doing to do this project for sure. Thanks for posting this.


    3 years ago on Step 9

    Couldn't you leach the background in a bathtub? Would make changing the water out a snap. Then after say a month of soaking you could put it in your tank.


    Nice BG. Depend how you build it but having a BG brings joy to you and the fish as long as you know your water parameters. Goodluck.


    6 years ago on Step 10

    Any chance of an update on how it's going, what you've done with your substrate and planting and the kinds of fish you've put in, any issues you found after running it for a while


    6 years ago on Introduction

    The instructable is great, but I wouldn't be a fish geek if I didn't point out that it is never, ever necessary or even acceptable to sacrifice fish to a slow burning torturous death from ammonia poisoning in order to cycle a tank.
    Ammonia burns the gills and if it doesn't kill the fish outright, it WILL reduce lifespan and increase likelihood of disease.
    Instead of torturing a fish, add a bottle of nitrifying bacteria, available at any fish store, and a pinch of fish food as an ammonia source. Test water. When there is no ammonia or Nitrite, only Nitrate, then the cycle is complete and THEN it is safe to add fish.
    I do love the river tank, though. Great use of concrete!


    7 years ago on Introduction

    Hi, great job on the background and good to know that the pH of the cement came down.

    I have 6 White Clouds myself, 2 being long-fins - I love these fish!

    You should look up "fishless cycling" for your next endeavor. It is a much less cruel process and pretty easy to accomplish.

    Good luck!


    7 years ago on Step 10

    COOL! easy to design and make, and cheap! love it! i will have to make one and include caves and ledges ;)


    7 years ago on Step 7

    [Excuse me about my english, I´ll try to do my best]

    Is this cement like Pegoland?
    Anyboy knows any similar product available in Spain?
    This is the one used by NaTeB1:
    And this is the one available at Spain:
    I don`t know if are tha same products.

    Este cemento es como el Pegoland?
    Alguien conoce un producto equivalente que pueda comprarse en España?
    Este es el que ha usado NaTeB1:
    Y esto es lo mas conocido en España:
    No se si será lo mismo.


    8 years ago on Introduction

    I am doing this at the moment with my 75 gal tank. Had to make two separate sections due to the glass support spanning the top. I as well found it easier to cut the rock first and glue it on. I am using a DIY foam cutter made from an old weller soldering iron and a piece of 12 gauge wire bent in a large circle put in place of the tip. Almost to the point of coating with cement now. Great instructible...too bad you beat me to it...:)

    9 replies

    Reply 8 years ago on Introduction

    I do hope you share your project... Mine isn't all that impressive when compared to larger scale backgrounds. I'm also having a lot of trouble finding plants because anything too big looks like a giant tree waving around in endless high winds.... What type of cement do you plan on using?


    Reply 8 years ago on Introduction

    A mason friend of mine gave me about 1/2 bag, way more then I need, of stuff called ultra tex decorative overlay (UT91-1 powder). He says it wont crack and he uses it on sidewalks and steps here in the harsh Michigan weather. Also says it wont leach once dried but I am trying to figure that out since its mainly portland cement and sand. It comes with its own wetting agent and I have a feeling thats where the strength comes from.


    Reply 8 years ago on Introduction

    Cool! Let me know how it works out. Mine has quite a bit of cracks but I kind of like it. Nothing major, I think most of them came from having to really force some of the pieces into place. Ill most likely end up with a larger aquarium... I gave up the hobby a while ago just had a sudden urge to do something with this 10 gallon Ive had sitting around. I always end up going nuts but hopefully I can keep myself in check.... Having a tiny apartment helps... Good luck and I really hope you will share your project.


    Reply 8 years ago on Introduction

    Have first layer of cement on...shaping up...not real impressed yet with the overlay stuff...some of its flaking off but maybe its because I mixed it real thin...Im letting it dry for a couple of days in the garage and will check it out then


    Reply 8 years ago on Introduction

    Wow! That looks really great! I'm thinking about redoing mine in solid concrete lol

    My first layer was really thin but I didnt touch it or move anything too much. But when I was working on the final layer I decided to coat the inside of the pump housing section just because the backside was open and it looked like crap. Anyway, this layer barely held up and a lot of it flaked off. Just by barely touching it, even just picking it up.

    I dont really understand the point of the first layer... But after the second layer it should be really solid. I wouldn't worry too much.


    Reply 7 years ago on Introduction

    Got my instructible up. Tank is up and running and I started cycling it. Now to build a canopy...


    Oh, Ill delete or you can delete this post if its too compeating with yours...


    Reply 8 years ago on Introduction

    I thought about just knocking the loose stuff off with a small brush before applying the next layer...if I dont the next layer wont stick. I think I may have mixed it a bit thin and let it dry to fast. I will let you know what happens and keep track of my work. The picts are of the whole thing but it had to be made in 2 pieces, which is a pain to coat in one layer at the same time but Im afraid if I dont it wont match.


    Reply 8 years ago on Introduction

    One thing, before I forget...

    Make sure you at least check pH! I know your friend said it will not leach anything but in every project guide I have read, including my own experience, the pH is usually off the charts. Especially during the first couple days. I'm sure you have already considered this but just in case...


    Reply 8 years ago on Introduction

    Yep I plan on checking and monitoring it..actually I am going to fill a couple of tubs of water and soak them in there and play with it there...dumping a couple of tubs of water would be easier then a 75 gal tank!


    8 years ago on Introduction

    This is wicked :P Do you have fish in there now and if so how are they with it? also, is the type of filtration you have set up needed? or can it cycle in any direction. Thanks again