Hey John,
I'll tell you a little story; A long time ago I was suffering chronic BGA. In those days I was still plugged into The Matrix and I was thinking that the BGA was due to too much nitrate so I kept measuring with a NO3 test kit and I kept getting high readings. I would add RO water and test as often as 4X per day. The algae refused to go away and I couldn't understand the high NO3 readings when I knew I was adding RO water. I was so programmed to trust the test kit that actually I started to distrust my RO unit. I actually went out and plonked down hard earned cash to buy a new RO cartrige. Same test kit results, same BGA. When I was at rock bottom emotionally, and there was no other option I decided to test the test kit, so I measured water coming straight out of the unit and it measure high NO3. I immediately went out an spent more money on a new test kit and finally it measured low that day. The next day I used the new test kit and I got a high NO3 reading. Reviewing what I had done I realized that I had spent over a hundred Euros + hundreds of labor man-hours. There was still BGA, and I still had no idea what the actual NO3 level was either in the tank, my RO container or in my tap. So yes, in my opinion they are as bad. They are your worst nightmare.
The problem with NO3/PO4 test kits are that they only occasionally tell you the truth. The problem is that one never knows on what given day the test is truthful and when it lies. You also never know how much it lies, so it can lie a little or lie a lot, so you can't even tell whether you're in the ballpark or whether you're in the next county. That makes them useless as far as I'm concerned. On top of that, if you fear nutrients then you respond inappropriately to their readings, so you wind up drifting further and further away from reality.
If you follow the EI or PMDD dosing principles you already know exactly how much ppm you have added that day or that week. If your tap water contains some then that's fine, because having more than you need is better than having less than you need. You also don't really need to worry about toxicity unless you're keeping trout or salmon. These are the only groups of fish that have demonstrated high sensitivity to NO3. Our fish have a very high tolerance, and I see no negative results after keeping generations of chichlids with high dosages of NO3/PO4. As I've pointed out many times, the NO3 is the smoking gun. By the time the organic NO3 levels build, the damage has already been done by NH4 and organic waste. When you do your water change, you are removing organic waste and are keeping those levels in check. It doesn't matter about you inorganically dosed NO3 powder. The fish don't care. Only your plants and BGA care.
As you've no doubt discovered, if your flow and distribution are spectacular, then it requires less of NO3/PO4/CO2 to keep the plants healthy. I'm not opposed to lowering the dosages at all. It's a great idea because it saves money and helps prevent unchecked growth, thus lowering maintenance. It's just that I know that most people have poor flow and poor distribution combined with too much light, which is the worst of all worlds. Instead on focusing on the real problems in the tank, they freak out about NO3, so they completely miss the boat. I've been there and I have the T-Shirt. I know this inherently. I understand
exactly how they feel. You have to suspend your fear of NO3 and trust in what you see. Be
consistent with your dosages and make a specific downward adjustment, say, 10% less. Then wait 3 weeks. If the BGA does not reappear then make another downward adjustment. At some point in your downward adjustment you will have violated the minimum threshold and you'll start to see signs of stress during that three week period. No problems, go back up to the previous higher dosing levels. Do your weekly 50% or more water changes, dose immediately afterwards and remove weak leaves and all loose organic debris. Organic waste is your enemy. Every morning I stick my hands in the tank, shake/fluff the plants to loosen weak leaves then I net any out. I'm very particular about this and it annoys me if I see even a single loose leaf floating about. Concentrate your energies on keeping the tank meticulously clean and forget about the illusion of NO3 toxicity. And throw those #£^%$ kits in the bin please.
Cheers,
