Dont realy want to dose Ei style just because i cant test the water
Like previously mentioned dosing EI is a workaround for not having equipment that can measure certain water parameters accurately without spending thousands of pounds on equipment and even if you could the results can change pretty quick. It may say what's in the water but if its in a form the plants can use is a different matter. PO4 can react with Iron and precipitate out which is why we don't mix macros and micros together and the reason water companies add it to our tap water to prevent lead poisoning from lead pipes as well as corroding metal pipe fittings, they also make iron precipitate out so they can filter it from the water. Your test may be saying po4 is in there but maybe in a different state. Also the test kit is heavily reliant on you making the decision on what it's saying. Depending what mood you're in will affect the result, if you think you must have low po4 and in the right light your kit tells you that you'll say "I knew it" Plus the kit in some cases like the HAGEN one measures up to 1mgl from nothing so how many shades of blue are there and could you differentiate between them? The amounts involved are so small I don't believe a test kit would know the difference.
With EI the whole point is Tom Barr has worked out that it doesn't matter how much light and co2 you put in a tank the plants can never use more fertiliser than we put in so as such it's a starting point for us all regardless of what lighting or setups we have.
If you want to roll back po4 the best way would be to start at EI levels and very gradually reduce it over time until you see a bad reaction in the plants. The downside of this is algae could attack before the plants show signs so you add more and have plants that are feeling a bit under the weather and algae mixed with loads of nutrients. The algae is going to grab them first and the long soul destroying battle with algae begins until you can reverse the situation and believe me algae are better at the game because they are not as fussy eaters.
So it's up to you which route you take, with EI your belt and braces safe as long as you have good flow to get these nutrients to the plants. Some tanks with poor flow may need more to accommodate that.
I'm not sure that trying to measure phosphates will give you any meaningful results, and it differs from NO3 etc in not being included in the water quality test results from your water company.
This was something I looked into a while back having heard my tapwater was full of po4 and indeed couldn't get results from my water authority. I gave them a ring and unexpectedly someone rang me back who was extremely helpful, we even ended up talking about fishkeeping! I suspect it was a lab rat who doesn't get out the lab much and enjoyed seeing the end result of what they were doing and thought for once someone is interested
😀 so if you want them you can get them.
In my area (North West) the water authority added 0.94 mgl to the supply on average in 2016, generally speaking she said that they add 2000 micrograms per ltr in the UK or 2mgl. Either way it's not a great deal but on Hagen test kit would be off the scale. You can sort of accept there is some in there and take it into account when dosing if you could be bothered I suppose.
The World Health Organisation recommends no more than 5mgl should be put into water supplies but I'm not sure if that's something all water authorities adhere to. That being the case even if they did, which is unusual, you would just in EI parameters without dosing any after a 50% change with tapwater. It's fair to say though there is no evidence that po4 has any health implications above 5mgl. It's mainly to stop phosphate entering the water system and destroying local water course with eutrophy (spelt wrong, going from memory
🙄) essentially promotes algae growth and increased plant growth which dies quicker than it can break it down>low oxygen>premature death to the water course.
For what it's worth the limit on no3 is 50mgl, Apparently this is to stop "Blue Baby Syndrome" where nitrate in the gut can turn back to nitrite and starve the oxygen. So unless the local water authority are up to no good the limits should be 5mgl po4 and 50mgl no3 which then brings me back to test kits when I hear people saying it's showing 75mgl out the tap.
I reckon anyone who has those parameters is in for a cheap hobby if high energy planted tanks are their thing. You could actually sell that in the lfs as "water for planted tanks"
🙄
Forgot to say... I think that's where the phosphate and algae confusion comes from when you look round sites. In a tank with no plants po4=algae, In a tank with po4 and no other nutrients=algae and po4 in water courses = algae but in the planted tank with thriving plants not so.
