Absolutely agree with this. I'm not sure 100% which is the physiological mechanism behind all this but in my mid light (70-80 micromol PAR) tank with good co2, see my ph drop below, dropchecker yellowish, etc. I never get rid of BBA in the old leaves or difficult areas of the tank (to the eyes of everyone it is a free algae tank, but not for a planted tank hobbyist)
http://www.ukaps.org/forum/threads/new-setup-from-2-to-just-plants.34374/page-2
IMO, EI recommended levels for PO4 (at least the ones in this site or Barr's site) boosts plants' growth very significantly, and once this nutrient is not limited anymore, CO2 is again the most limiting or at least the most difficult parameter to meet... Probably to high biomass to be fed? To more difficult flow due to the biomass growth? not really sure, but it seems that good CO2 is more difficult to achieve and BBA appear.
I have noticed significant changes just using an EI method with lower PO4... Let's say adding 1 ppm instead of 3-5 ppm of PO4. My previous light and my previous CO2 (according to ph drop should be around 30-40 ppm) is now perfect and the tank looks nearly algae free.
Ok, once we are here (nothing new for most of you I'm sure), the answers would be:
- 'that is because you have too much light'. And my reply would be that reducing light is the key points of course, but not only for EI but for all the planted tanks methods. The fact is that now my light is the same and co2 demand is more feasible
- 'EI never said to use fix values, just decrease the amounts use until you notice side effects'... Ok, so we are not in that method of unlimited amounts, we are getting close to other approaches, such as PPS-Pro. Anyway, I don't care which name or brand the method has, but if we have to decrease to adjust the system, IMO the method lose part of its point
- 'you need more co2'. I think I am not a newbie on this. I've been fine tuning my setup for two years, my estimations of CO2 (I don't own a co2 meter) all seem to point in the right direction. It also amazes me how high co2 has to be in most of the high light EI tanks... Because CO2 is by far the most difficult issue in a planted tank. So a method that was intended to be for the newbie (no test, no accuracy in dosing...) ends up with super demanding co2 levels (agree that mostly when playing with high light)
- 'you blame PO4 and it is demonstrated that PO4 is not responsible for Algae'. And I totally agree. It is not PO4 to be blamed, umy guess is that PO4 high levels drives to very demanding CO2 levels which are very difficult to achieve. Therefore PO4 do not create algae but creates an scenario in which BBA can easily appear.
Of course I may be wrong in some of the assumptions I made and I would be very happy if someone can point out why I am wrong.
Jordi