Redfleld Ratio - This post is from just a month ago and saves me a lot of typing
http
/www.fishforums.net/index.php?/topic/336801-the-redfield-ratio/page__hl__redfield__fromsearch__1
This hobby has come on a long way in the last few years alone in terms of understanding what to do and whats actually going on. Redfield is pretty old. Ignore ratios, just do what the plants need and not what someone thinks they need.
P can be as high as you want it. The reason we tend to limit it below a certain level is because it reacts very easily with Fe. The more P often means cloudy water as it reacts with the Fe and locks it away. It isn't anything to do with a N P ratio. We will normally be doing circa 1:6 and not 1:10 but as above this is not fixed. Some may do 1:3 Some may do 1:20. No rules here.
The article said not to change water often but to add N/P instead.
I do no water changes and only NP every couple of months IF necessary.
I took a conclusion that there was heavy imbalance in my water quality, I bought a P test kit and it did spike heavily.
Thats why we don't test. Testing parameters with hobby test is a recipe for disaster in many cases. Inaccuracies, false readings, acting on old info etc can be the bane of many people's tank.
So I did a reset to the water first trying to reduce my P to acceptable level, afterwards I don't really need to play with chemistry set and the algae growth stops.
How much P do you think is already in the tap water? If you have a planted tank and it uses P, then doing no water changes would in essence (apart from that in fish waste and food) mean you reach zero, just as nitrate. Water change will replenish, not reset. However if you are following a no water change regime and using the fish waste and food as your source of N and P, what is the difference? Just means unbalancing what was stable. i.e. the tank had set its parameters over the space of time and then suddenly fresh tank water with a huge difference in all paramters including KH, Ph and nutrient levels is added in. Makes no sense to me if we are using it in conjunction with the redfield argument.
I could understand it as feasible if we are resetting with RO water and then adding the N and P as that would be a reset of sorts but to just ad tap water in is adding an 'unknown' in terms of content and therefore any ratio is out of the window.
I understand the common understanding for people are P = bad = algae and the other group say P = good and needed.
Wrong way round here. People who are serious with planted tanks already follow
NP = good. those who have little interest in the plants other than decoration are in the main
NP = Bad
I think both are right, P if kept under control (Should not be 0) does not create problem.
The only problem you will have with P is if there is a reaction with Fe. The level that are suggested for 'keeping it under control' are way lower than any problem area IMO and others. Problems normally arise when people try and micro control things like nutrients because they fear old understandings.
Adding fertiliser depends on what fertiliser my further push your imbalance.
Only things that controls what fertiliser is added are:
1 - The type of tank - Light levels, CO2 addition, regime etc.
2 - The content of the fertiliser. Does it have N and P in it? Does it fit the type of tank?
What helped me really is that I went the hi tec way before coming to non CO2. I learnt to push things first and then was able to lose any fears I may have gained from researching non CO2 first. Then I can take on the non CO2 approach with no fear of N and P neither in their ratio or concentration. It also taught me to trust the water parameters and not to play with them. Let the water go where it wants and not worry about a parameter changing over time.
I think those who go the other way round often have a bit of a handicap as they research low tech methods and the majority of those are written by long term old myth believers. The world is slowly changing though
AC
Trouble is the more you read the harder and more expensive it all seems to become 
