Should I start dosing phosphates ? How ?

Idech · May 3, 2022

My tank is a 75 gallons, 7 months old LPS/softies tank. I have 25-30 corals.

Here are my parameters :
Salinity : 1,025
PH : 8,1
Calcium : 420
Mag : 1340
Alk : 9,5
Nitrates : 16,3 (slowly but steadily dropping)
Phosphates : 0,02 (steadily dropping and expected to be 0 in a few weeks)

Here is a phosphates/nitrates graph :

Should I start dosing phosphates now to avoid algae/dinos problems and have enough nutrients ?

What should I buy ? I’m very wary of adding any chemicals to the tank. I don’t mind paying more to get a reliable product.

Thanks !

gabedickerson7 · May 3, 2022

I personally have never had to dose phosphates before. All I have ever done is change how good my export system is working. This for me meant to put my protein skimmer on a cycle and not leave it running all the time, reducing the amount of light my chaeto gets, as well as feeding more when needed. Not too sure how your system is set up but I have also noticed my pellets that I feed occasionally seem to have more phosphates than my frozen mysis that I feed so maybe start there? Good luck.

ChrisRD · May 3, 2022

How do your corals look? Do you have a decent fish load in the tank? Feeding fish regularly?

If so, and assuming you're not driving nutrients too low with phosphate media, bio pellets, etc. I don't think I'd be too concerned with NO3 or PO4 numbers. Keep in mind you can read "0" on test kits and still have enough of these nutrients in the water to have plenty of algae growth (and healthy corals).

I might be more outdated with my thinking on this stuff (started the hobby in the 90s) but IMO If it ain't broke...

Idech · May 3, 2022

ChrisRD said:
How do your corals look? Do you have a decent fish load in the tank? Feeding fish regularly?

Corals all look fine except one frogspawn that has always been picky and is staying small.

I wanted a small bioload so I only have 6 fish, the biggest one being a kole tang.

I feed them frozen mostly, twice a day. Reef roids once every 7-10 days.

ChrisRD said:
If so, and assuming you're not driving nutrients too low with phosphate media, bio pellets, etc. I don't think I'd be too concerned with NO3 or PO4 numbers.

I don’t have a sump so nothing like that. Just a skimmer and internal filter with filter floss that I change every 5-7 days.

ChrisRD said:
I might be more outdated with my thinking on this stuff (started the hobby in the 90s) but IMO If it ain't broke...

I like outdated, lol ! Thanks

gabedickerson7 · May 3, 2022

ChrisRD said:
How do your corals look? Do you have a decent fish load in the tank? Feeding fish regularly?

If so, and assuming you're not driving nutrients too low with phosphate media, bio pellets, etc. I don't think I'd be too concerned with NO3 or PO4 numbers. Keep in mind you can read "0" on test kits and still have enough of these nutrients in the water to having plenty of algae growth (and healthy corals).

I might be more outdated with my thinking on this stuff (started the hobby in the 90s) but IMO If it ain't broke...

I personally believe that nitrates around 8-10 and phosphates around .02- .04 are solid numbers. I test bi weekly and if my numbers drop below or above that range I will change something. I feed my fish once a day with frozen mysis and occasionally feed pellets. I recently upgraded to a 150 gallon tank and have a sapphire 34 sump with reef octo 150 INT. I recently put in a purple tip hammer that is doing great.

ChrisRD · May 3, 2022

Honestly, your parameters and feeding schedule seem fine to me. If everything looks good I don't think I'd do anything different at this point.

Years ago everyone was striving for "0" N levels and nobody even seem to care about P. The current thinking seems to be that we should dose to maintain certain levels of these nutrients. I'm no expert but it's hard to ignore all of the years of thriving reef tanks where folks never did this and had "undetectable" levels of these nutrients. I think the coral nutrition topic is probably a complex one but it seems to me if you're feeding enough (including fish poop) that is probably more important than the residual N / P levels in the water (at least what we can test for with our hobby grade stuff) .

Just my $0.02 of course...

Idech · May 3, 2022

ChrisRD said:
Years ago everyone was striving for "0" N levels and nobody even seem to care about P. The current thinking seems to be that we should dose to maintain certain levels of these nutrients. I'm no expert but it's hard to ignore all of the years of thriving reef tanks where folks never did this and had "undetectable" levels of these nutrients. I think the coral nutrition topic is probably a complex one but it seems to me if you're feeding enough (including fish poop) that is probably more important than the residual N / P levels in the water (at least what we can test for with our hobby grade stuff) .

That’s reassurance enough for me. I feel safe doing it if it had been done dozens of years with success. I’ll ignore the new ways for now and just go by how the tank is doing. Hopefully if anything derails, I’ll catch it before it‘s too late.