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.
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.
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.