How to Make a Blackwater Tank
by Josh Day
So you've decided to go for the natural south American river basin look for your discus or tetras, or you want to make your tank more acidic and induce breeding. Perhaps you just like that tea-colored look... whatever the reason, you'd like to make your tank a blackwater biotope.
Here is what mongabay.com has to say about the blackwater biotope:
"Blackwater ponds, creeks, and rivers originate in the rain-forest. In the slow-moving waters, acids are leeched from decaying vegetation creating very transparent, tea-colored water. These waters have almost no measurable water hardness and an acidic pH.
"The substrate in blackwater habitats is typically leaf litter over a base of fine clay or sand. Decaying wood and plant matter is common especially in flooded igapo forest. There are many submerged terrestrial plants, many of which retain most of their leaves." *
Blackwater is made by tannins, the substance that is released by driftwood, leaves, peat moss, and a variety of other natural substances. Oftentimes, many people strive to make their tanks sparkling clear and remove the tannins--this is done by boiling driftwood from 2-12 hours to remove most of the tannins from the wood so they will not heavily leach out into the tank water. However, probably the most effective substance in removing the tannins is carbon.
Needless to say, you must remove the carbon from your filter in order to make a true blackwater tank. (Sidenote: if you only want to lower your pH, add peat moss to your filter without removing the carbon and your water will not tan.)
Before we discuss the carbon removal, let's talk about adding the tanning substances first.
Driftwood is a good source for tannins. To remove the bacteria or insects from your wood, boiling is needed, and this also helps to waterlog your wood. Over time, depending on the size of the piece, the wood will release tannins into your water, lowering the pH and giving your tank a "tea" color look.
Unfortunately, driftwood does not always give off enough tannis. This may be due to your piece being boiled too long, it is too small, or you are running carbon in your filter. This is why peat moss or oak leaves can be employed to really tan up your tank.
Peat moss can be purchased at most general hardware and outdoor stores, as well as any garden shop. You want pure peat moss with no soil additives--Sphagnum peat moss is a good brand, but they also sell something called Sphagnum moss, which is ornamental moss for hanging pots which you definitely do not want. Peat moss is cheap; you can get about twenty pounds of it for four or five U.S. dollars.
Now that you have your peat moss, your next step is checking your filtration. Are you using carbon? If so, it has to be removed. Unfortunately, many filters like Marineland's Biowheel series filters do not allow you to easily remove the carbon from the cartrides, so some do-it-yourself work is in order here.
Here is a website which will illustrate how to remove the carbon from a sealed cartridge.
And here is the article in its full text form by Off-Ice, sans the pictures.
"I use a Penguin 330 HOB filter on my 55g tank. I did not want any carbon in my cartridges, and for those who have to buy these, you know how expensive they can get. So this is what I came up with. I use the same procedure for my Eclipse 2 filter cartridges. I believe this will work for the Emperor filters as well, but as I do not have one, I can't say for sure.
"First thing you need to do is get the cartridge and remove all the blue padding and carbon. You will need to cut notches in the side of the frame. This will aid in attachment of the new fiber, and allow the frame to slide into the grove in the filter.
"Now you need to cut the new fiber. I used 100% polyester fiber matting. You should be able to get this from a craft store or Wal-Mart. Make sure it has no additives (perfumes, dyes, ect.)
"Now all you have to do is attach it to the frame. I use rubber bands. When I replace the matting, I also replace the rubber bands. They are cheap, and tend to degrade in water.
"Simple as that. A roll of fiber matting is only a few dollars, and will make quite a few replacement cartridges."
(Source: link mentioned above. Article published by plantgeek.net)
Polyester batting is the substance that makes up the Tetra Whisper filter cartridge. It is also that fluffy white stuff you find at the fish store called "filter floss" or "filter fiber." As the article above mentioned, you can get the same stuff in sheets or fluffy mounds at Wal-Mart or most retail or craft stores for much cheaper.
This will solve your problem if you're using HOB filters. However, if you're using a canister or wet-dry filter, some more work is in order.
Be sure to either boil your peat or rinse it very well once it's loaded into the cartridge or media venue.
Your tank should start to take on the tea look within a few days. Be sure you have a pH test kit to monitor the level in case it drops too low for your fish. If you find it getting too low, stock your filter or tank with calcerous substances--like seashells, certain types of rocks (limestone), and best of all, crushed coral or coral sand you can pick up at the fish store--be sure to load these into pantyhose or other pockets of batting in order to remove them later.
If you elect to use leaves--either in a media venue in the filter or in the substrate itself--watch out for decay and their fibers flying all over the tank. If you go for the substrate, be extra vigilant. As always, boil your leaves before placing them in the aquarium.
There is also a product sold called Blackwater extract. Generally, this product is frowned upon. For more information, go to http://www.thekrib.com/Chemistry/humic.html
Good luck with your blackwater biotope, and happy tanning!
*A Place Out of
Time: Tropical Rainforests and the Perils They Face