Optimal phosphate levels in a planted tank

[Firestorm]

This is my 40 gallon breeder tank. I recently (< 3 months ago) started injecting CO2, but at a slow rate of ~1.5 drop per second. Not enough to turn the checker green (more than that, and the fish gathers at the surface), but I am ok with that since I don't have "picky" / difficult plants. So, I just took the checker out, and keep it at the same slow rate.

This tank has been having green spot algae (GSA) issues since the beginning (I started it in July 2021). After I started injecting CO2, I started using Thrive fertilizer (I bought it back in 2020, but did not like using it since it appears to trigger GSA in my previous tank. But now, when CO2 is injected, I feel like I have to use it. Although, I do use it very conservatively, usually only about 2 pumps after a water change. I also add a very conservative amount of Seachem Potassium, Iron, and Flourish/micros. The thinking behind it is that fish provides additional macros, thus dosing a whole lot of Thrive doesn't really make sense, and adding micros should make nutrients more usable to plants (d/t correct ratio).

As of last week, it was suggested to me that increasing phosphorus can help with GSA. I ordered Seachem Phosphorus and dosed only about 1/3 of the recommended amount (since I dosed it on top of Thrive). For some reason, a few of my platies--born and raised in this tank--started showing signs of distressed: Flashing, semi-clamped fins. I am a bit worried that phosphorus supplementation might be to blame since this is what changed. I measured phosphate level with API phosphate kit, photo of the result is below. It looks like it's 1.0 ppm. Can dosing phosphorus bother fish and cause it to flash?

I also checked ammonia and nitrite just in case (yesterday and today), and both are at zero.

I am not used to seeing my fish flashing, and it is very upsetting and alarming to me. Please help me figure out what's going on. What is a proper PO4 level?

Thanks in advance!

 

[*Ci*]

FWIW, the phosphate level in the tap water that I use for my tanks is 5ppm. I have no gsa and no distressed fish, but maybe it was just the sudden change that affected yours?

 

[Firestorm]

I wonder if phosphATE in tap might be different than the Seachem Flourish PhosphorUS that I am dosing. It would make sense that an element (phosphorus) might be much more reactive / have different chemical properties than a compound (PO4).

 

[Burr740]

In any reasonable amount PO4 should have no impact on livestock. Most high energy tanks roll with 5-10 ppm

Seachem Phosphorus is nothing but potassium phosphate

Seachem - Flourish Phosphorus

www.seachem.com

 

[Firestorm]

Thank you so much!

 

[BigWave]

Thrive is a well ballanced fertilizer based upon the ei method. So it should provide everything your plants need. You should not have to dose Seachem along with Thrive. Simply up your dosage if your seing GSA.
Something else is going on with your fish. How much surface adatation do you have? The water surface should almost be rippling and or chopping.
Often times the stress of higher CO2 levels or parameter changes causes distress and whatever disease mostly ich shows it head. Watch the fish closely.

 

[Firestorm]

I thought I'd update this post of mine. Turned out, Hikari Ultimate was the cause of this short-lived nightmare. I switched back to Prime, and things have completely normalized. Thankfully, no fish losses. Thank you so much everyone for the support.

 

[BigWave]

Turned out, Hikari Ultimate was the cause of this short-lived nightmare.

Interesting.