When I kept BW tanks I used Ketapang/Indian Almond leaves, far more natural, and IMO far better for your fish than the salts/preservatives and petroleum based dyes found in most of the mass produced products.
As an example;
MATERIAL SAFETY DATA SHEET
PRODUCT: MICROBE-LIFT Amazon Bio-Colorant
http://www.microbelift.com/files/1312/6928/7969/MSDS-AMAZON-BIO-COLORANT.pdf
Are these substances that ones fish should be bathing in 24/7?
Cellulase, Citric Acid, C.I Acid Blue 9, Disodium Salt, FD&C Red 40, FD&C Yellow No. 5 (Tatrazine), Potassium Sorbate 2, Sodium Benzoate.
FYI - Red 40 is banned in Denmark, Belgium, France, Sweden and Switzerland. Yellow No. 5 is high on the hit list as well, plenty of controversy surrounding the use of both of these dyes. What their long term effect are on the overall health of aquatic organisms is anyones guess, as there is no data to determine any type of safety margin.
The same company also markets & sells;
MATERIAL SAFETY DATA SHEET
PRODUCT: MICROBE-LIFT Amazon Black & Soft Water Conditioner
http://www.microbelift.com/files/3712/6928/7970/MSDS-AMAZON-BLACK-SOFT-WATER-COND.pdf
Problem is, other than stating that this formula consists of 85% water, the rest is a guessing game as the manufacturer lists the
active components as proprietary. Fair enough, I understand the need to protect ones "trade secrets", but this is coming from a company that makes another "Amazon Black Water" product, that is far from what I would personally consider green, earth friendly, or proven to be safe for long term use on aquatic organisms, including fish.
In the above MSDS it states: "Rubber gloves not necessary but recommended." and yet also states: "May cause infection if in contact with open wounds."
I'm not one to go off on a tantrum over what is sometimes stated on an MSDS, I'm trained in this area and have been reading MSDS sheets since they originally came out many years ago, but at the same time I don't get a warm fuzzy feeling when ingredients in water additives are hidden whenever possible, when that same company uses ingredients such as Red # 40 & Yellow # 5 in another Amazon product of theirs.
I suspect that if your fish could talk they would say **** all that crap, keep it natural bro.
For those not familiar with Ketapang leaves ............
http://sarawakmedplants.com.my/inde...ts-list&rid=293&rllabel=More+Details&Itemid=4
Ketapang (Terminalia catappa) leaves have been used in SE Asia and elsewhere among fish keepers for their antibacterial, antioxident, and antivirul properties for decades. IMO this type of BW (tannin from leaves) method is not only more natural, it's also far better for the overall health & well being of fish that come from a black water environment.
HTH