Brian, do you have invertebrates?
There are some treatments that will kill BBA. However, in most cases the best approach is one that attacks on two fronts. The first being getting everything lined up in order as far as water parameters and nutrient levels and then culling infected leaves. Secondly is adding a population of BBA algae control specialists. Assuming you do have some invertebrates let me lay out the method and technique to ridding your tank of BBA.
levels in your tank so that they are always within the range of 20-30ppm throughout the photoperiod. In most cases this is the culprit as in many cases determining CO2
levels is problematic. To make certain your readings aren't being skewed by another acid or base you need to check your water parameters. Take a quart or so of water from your tank and leave it in a bowl overnight. Perform a pH and KH
test on this bowl of water the next day. Record the results and compare to a CO2
chart. If the results show more than 2-3ppm of CO2
you have something causing an interference in getting accurate CO2
levels. Post back and I can help you with a guesstimate procedure.
Proceed to step 2 only after you are certain you have properly solved step one.
Trim away BBA infected leaves. If this means you will be trimming away more than 50% of the leaves then you should trim away only the worse 50% infected leaves. Always leave at least two leaves per plant. As soon as new leaves begin to grow out start removing the other infected leaves...this needs to be done no less than twice a week, daily is better.
Immediately after preforming step 2. Do a 50-70% water change. After the water change add 10 ppm
in the form of KNO3, 15 ppm
of potassium in the form of KCl or K2SO4, and dose a trace nutrient provider like TMG, Flourish, or Plantex as per the recommended amount. Don't dose PO4
Add a BBA control crew consisting of true SAE
's (at least 1 per foot of tank length), Amano Shrimp, and Rosy Barbs. Long finned Rosy Barbs are the preferred choice as they are slower and don't have as much dither factor. Rosy Barbs are excellent BBA eaters.
Repeat steps 2 and 3 at least weekly, twice weekly is preferred.
This method has worked for me many times on many peoples tanks both locally and online though forum help. It is very critical that each step be done correctly. You are correct, there are many species of each type of algae. Spores are everywhere and short of pulling and bleaching everything every few months algae is impossible to kill and not have again. The best approach is to eliminate it visually and then make sure to keep the tank running with an environment that favors plant growth over algae. If you consider where algae's niche is it makes it easier to control. Algae flourishes when water contains high amounts of organic water, ammonia/ammonium even in trace amounts, stagnant water, water with very low CO2
levels, or water that contains little plant nutrients. Notice than you will often find a pond with algae growing rapid yet no fish...algae gets by on several orders of magnitude less nutrients than plants. So it should stand to reason that algae occupy a different niche than plants and strictly speaking plants and algae aren't competitors for the same nutrients so limiting nutrients will only limit plants.
Once the BBA is gone you will probably begin to see GSA. GSA is a sign of a healthy tank and in most cases maintaining a bit higher ratio of NO3
will eliminate this innocent algae.