Hello all! I am currently setting up a 10 gallon blackwater tank - defined herein as a tannin stained tank with PH 6 or less and with TDS, KH, and GH as close to zero as possible. The issues with such tanks have been repeatedly mentioned elsewhere, but I wanted to go on a different track and extol their virtues. Here we go!
The fish -
This is why these tanks exist! Some fish cannot survive in captivity without these kinds of tanks; many others (neon tetras come to mind) will not breed without them. This, by itself, is a big plus...BUT there are many more
No New Tank Syndrome -
As many of you know, ammonia exists in two forms in the aquarium - NH3 (the dangerous form we all worry about) and NH4 (ammonium, which is essentially harmless). The relative amounts of these forms depends on PH...and, at a PH of 6, you would need over 5 ppm total ammonia (both forms of ammonia combined) to produce the needed .03 ppm NH3 needed to begin damaging fry. You have even more margin for error as the PH drops! Needless to say...you are NOT likely to kill fish in a blackwater tank with traditional new tank syndrome! (This compensates for the fact that the denitrifying bacteria often struggle to get established in very acidic tanks)
Ample CO2 -
In hard water tanks, much of the CO2 that enters the water gets converted to carbonates that plants have to waste energy to extract the CO2 out of. In blackwater tanks, that CO2 remains as either CO2 or carbonic acid, both of which are far easier for plants to use.
- Not all plants adjust to the nutrient-deprived, highly acidic blackwater tank; however, those that do fare quite well (and MANY plants adjust just fine...I've found dwarf water lilies, java moss, water lettuce, cabomba, sunset hygro, java fern, creeping jenny, and others adjust fine and often grow much
faster than in normal tanks. The water lettuce even outcompetes duckweed in my ph 4.4 licorice gourami tank!)
Little/No Algae! -
Real blackwater tanks have a shortage of light AND nutrients, and have copious carbon dioxide...needless to say, unless you are giving it far too much light, algae is seldom a problem in these tanks. As a person who struggles with algae in most other tank, this is a big deal!
Well...that's me singing the praises of blackwater for now. Thankx and enjoy