Phosphate test kit questions and suggested PO4 levels in tank?

Question:

I have the high sensitivity kit which you have now discontinued and have seen the new kit which has been released. In the old kit the instructionssay to use the P readings and not po4 whereas the new kit uses po4. The kit says that we should maintain the p level below 0.015 which is 0.046 P04 but the new kit says to keep it between 0.04 and 0.25 p04 which is a massive difference to the old kit.

I find this very frustrating and confusing as i have no idea what level i should maintain. I had been keeping my tank at 0.015P as per the instructions and have been suffering with algae and had been wondering whether this was too low which is causing the problem. Can you please confirm what i should be aiming for

Gary

Answer:

Hi Gary

For Small Polyp Stony corals(sps) you should be maintaining PO4 ideally below 0.04ppm(which you are).

More tolerant Large polyp Stony coral ( LPS) should be fine up to 0.1ppm PO4 but in the main

you will need to keep at or below 0.04ppm PO4 to keep SPS corals and maintain good colouration.

Soft corals are the most tolerant and can grow in quite high PO4 concentrations of up to

0.25ppm although this doesn't mean its a good idea to run at those levels.

So to sum up with both old and new kits we should be looking at an ideal range of around

0.04ppm PO4. Higher ranges can be tolerated by different corals but for arguments sake

try and keep PO4 between 0 - 0.04 ppm for best results all round.

Try not to achieve absolute 0 however as this in itself can rob corals of PO4 which they do

need at very low levels for cell production, this is the same for all living things.

Algae can often grow at very low levels of PO4 if PO4 is tied up within the substrate or there is

enough NO3 present to fuel growth.Bryopsis algae for instance can fuel its own nutrient requirement

from trapping detritus and removing PO4 on site. Cyano algae's by contrast can remove

gaseous nitrogen directly from the water. Both kinds of algae can manage this with very low

levels of NO3 and PO4 in tank and require different approaches to rid them from the aquarium.

Regards and best wishes

Tony

Response:

Hi, thanks for the quick response but I am still confused with the different scales between the new and old kit. On the old kit is P actually po4 and is po3-4 the same as p-po4?

D-D response:

Hiya

The kits have caused a little confusion as on the old test PO4 is second from the top of the test colour strip and on the new kit the PO4 reading is at the top of the test strip. PO4 3- and PO4 are the same thing i.e they both express the Phosphate ion.

The new kit refers to Phosphorous as P-PO4 i.e reporting Phosphorous concentration derived from Phosphate PO4/3.07 = P.

So on the old kit aim for between 0-0.046 Phosphate (PO4 3-) or 0-0.015 Phosphorous(P)

New kit aim for 0-0.04 Phosphate (PO4) or 0-0.013 Phosphorous (P-PO4)

I usually sit between 0.024-0.046 Phosphate (PO4 3-) on the old kit and between 0-0.04 Phosphate(PO4) on the new kit and this works well for me.

Hope this helps

Tony