Hello all! Here goes nothing. :biggrin:
After reading and rereading the wealth of information in this forum, I realize I have made mistake after mistake in my so-called planted 7 gallon. I didn't plant heavily from the start. I didn't use enough/ correct substrate. I underdosed nutrients. I performed massive water changes. Thus as I approach this tank's one year anniversary, my betta is glowing and in good health, but my plants (2 crypts, a red tiger lotus, several sad clumps of sagittaria, two stands of rotala rotundifolia, two stems of limophilia aromatica, and most recently, a few stalks of ambulia) are being smothered by cyanobacteria. Lighting in this tank is a lowly 13W CFL.
In a perfect world, I'd move everything to a 20 gallon and start over the right way. Not an option. Welcome to the world of cluttered apartment living.
On to my question. After siphoning out as much BGA as possible on 5/26, I slowly built up my nitrate reading from 0 to about 5ppm using a KNO3 solution, dosed Flourish and Excel at the recommended rate, and increased water circulation. I also placed half a Plant Tab each underneath my ailing sagitaria and lotus. Over two weeks, I had no recurrence of cyano on the tank glass, but noticed very little plant growth either. Cyano growth on plant leaves slowed, but clearly never completely stopped.
What I did next has caused all hell to break loose.
Thinking that DOC's might be one culprit for the cyano (unlikely now that I look back on it, since I never let up with WC's) I had added carbon to my filter for about a week. Sure now that my DOC's were next to nil, I removed it. Thinking that I had things well enough in hand to let the plants rip (nitrates and plenty of traces in the water, good water movement, etc.) I hooked up a fresh 1 liter DIY CO2.
I wake up to cloudy water, since removing the carbon took out a growing bacterial colony. :iamwithst: And an insane amount of freshly grown, pearling BGA. (Incidentally, this is why I could never improve at chess. I can study something a million times, and still screw it up in an applied situation. I should have KNOWN my filtration was going to suffer, I've read so many posts about rapid media replacement...)
So my analysis of the situation is this. Having allowed a substantial amount of BGA to grow in my low light tank (enough to at one point cover most of two sides of a 7 gallon and multiple plant leaves; being new and not knowing what this junk was, I really stretched the idea of "living with" it) running CO2 gives an edge not to my beleaguered plants, but to cyanobacteria, since it has colonized my tank to the extent that it is now the dominant plant life. I'm guessing that the low level NH4 outbreak, not observable on my test button but obvious from the cloudy water, was also absorbed to a certain extent by the algae, fueling the rapid expansion. More absorption of nitrates and other nutrients takes place, and any dead or dying leaves then leach more. The cycle would continue until I'd have no higher plants left.
I really wanted to avoid it, but it looks like I have no choice but to go the Maracyn (or blackout) route, just to reset the balance. But in a perverse way I'm glad this happened, because I've read so much this week.
In case you read this Mr. Barr, I have done my damndest to apply the ideas you present so strongly in the "outcompete" thread to figuring out my own, latest failure. I may have to resort to chemicals to give my plants a fighting chance in the short term, but I'm not done trying to get them growing the right way. Even if this 7 gallon is never perfect, my tanks down the road will benefit. Your forum crusading is much appreciated.
