That's not what I said at all. What I actually said was that the total nitrates from all the potential sources could add up enough to cause a problem for the fish. So, if you already have nitrates that are 'off the chart' then adding more via fertilisation was unnecessary and not going to help the issue.
Hi tam,
What I am saying is that:
1. You actually you cannot tell from a nitrate test kit how much NO3 is in the water. There may be up to 50ppm as limited by Euro laws in the tap, or there may be zero. A hobby grade test kit cannot give you reliable information as to what the concentration level is.
2. Even if the tap water is at it's maximum, adding more NO3 will not cause any more toxicity. The level of toxicity NO3 possesses is in the hundreds of ppm and and almost to the thousands of ppm.
Furthermore, if you are lax in your water changes, the toxicity to your plants and animals has nothing to do with NO3 concentration. The toxicity arising from pollution has everything to do with hypoxia as the bacteria will steal oxygen from the water.
The fish, therefore will die outright or will have long term damage from loss of oxygen, Ammonia and Nitrite poisoning long before they will ever encounter any effects of NO3 poisoning. These toxins are thousands of times more fatal to fish that NO3.
What we have been trying to say is that NO3 is natures way of DETOXIFYING the environment, not the other way around. By the time you have accumulated 250ppm of NO3, the damage to the fish has already been done by the concentration levels of the toxins NO3 is meant by nature to neutralize.
When thinking about the health of your tank, NO3 is one of the very last components you should think about because it's presence in the water colum is a smoking gun and it indicates that the toxic bullet has already been fired. The fish have already been harmed and the NO3 is merely a residue of the attack.
NO3, as I am sure you are well aware, is the end product of the nitrification cycle. NH3/NH4 --> NO2 --> NO3.
What is much less well known (or which is never thought about) is that the aerobic bacteria that are in involved in this detoxification cycle use a tremendous amount of Oxygen to achieve this.
That's where the Oxygen goes. The "O2" in NO2 is Oxygen and the "O3" in NO3 is 50% more Oxygen.
This is the same Oxygen that the fish would have been breathing, but no longer have access to because it is tied up in the NO3.
When we add KNO3 to the tank it is already NO3. There is no conversion which steals Oxygen from the water column, so this has no impact on the fish.
The more pollutants that build up in the tank due to lack of water changes the more the bacteria will act on them and the more Oxygen they will steal from the water. As more and more Oxygen is stolen the less healthy the fish become. However, in a planted tank NO3 feeds the plants and so all other things being equal, during the day, if the plants are healthy then they will produce Oxygen and will replenish the Oxygen supply stolen by the bacteria. Unfortunately, they do not produce Oxygen at night and they compete with the fish for Oxygen. The bacteria never stop their activity so that at night fish, plants and bacteria deplete the Oxygen supply.
Water changes, gravel cleaning and filter cleaning removes the pollutants upon which the bacteria act. So this is what people need to worry about. They never need to worry about adding NO3 to the tank. They DO need to worry about hypoxia and the problems that occur as a result of hypoxia.
Hobbyists having overstocked tanks and who experience lax water changes have much more to worry about therefore, than how much NO3 is in the tank.
Nitrate is not toxic, but the consequences of pollution definitely is.
Cheers,
