Dosing Phosphate

[Red Firefish]

Hi everyone. I posted this in the plant forum in more detail, but thought I'd ask a larger audience:

Does anybody dose phosphates to their reefs to supplement photosynthesis? I'm referring specifically to using it to stimulate algae growth in the refugium setting, but I suppose if anyone was phosphorus-limited in their reef they might have a way of dosing it.

Is there a supplement that people prefer over Seachem's Flourish phosphorus? Thanks all!

[SeanT]

Do you add iron as well?

[Red Firefish]

I've thought about it, but I don't dose it regularly. I don't have an iron test kit that I trust, or a pure iron supplement (Seachem's Flourish Iron is Iron gluconate, which I believe is organic). I do weekly water changes with a blend of Oceanic and Instant Ocean salt, both of which contain iron.

Also, if I were to overdose iron, there isn't a convenient chemical resin to remove it, so I'm a bit more wary of dosing it.

[wrott]

There is so much phosphate in food that the answer to your question is yes, 2 or 3x / day. I feed flake, pellets, frozen--several varieties of each. And I run a phosban reactor w/ lots of algae growth.

[adtravels]

again I dose phosphate twice a day, flake in the morning, frozen in the evening

[King-Kong]

I'm pertty sure your in-home reef is never short on phosphate.... not much is needed, and we tend to have way more than we need.

Now as for nitrogen and carbon.. that tends to be a bigger issue.

[Zifer]

i would not do it..doesnt sound like a good idea...

[Flint&Eric]

depending on your N or P levels, whichever is limiting can be dosed to increase chaeto growth and lower the other.

e.g. Nitrate's are high but po4 is low. If proper flow and lighting is given to the chaeto, a small amount of Kpo4 can be dosed into the refugium allowing the chaeto to uptake the dosed po4 and the no3 that's produced by the tank.

hth.

[pkmg]

Dosing phosphates and Nitrates is done with planted aquariums for the goal of reducing algae growth. Basically in the past few years it was found that in ideal conditions the plants will out compete the alge for the nutrients, and that doses will even reduce algae growth.

I do not believe you could create the same relationship in the reef aquarium.

[Red Firefish]

Originally posted by Flint&Eric
depending on your N or P levels, whichever is limiting can be dosed to increase chaeto growth and lower the other.

e.g. Nitrate's are high but po4 is low. If proper flow and lighting is given to the chaeto, a small amount of Kpo4 can be dosed into the refugium allowing the chaeto to uptake the dosed po4 and the no3 that's produced by the tank.

hth.

That's exactly the idea. It's been about 6 months since I began doing it. Nitrates weren't high before (around 10), but after adding the plant tank to the system it kept climbing while phosphate stayed undetectable. Dosing phosphate dropped the nitrate to less than 0.2, so I think it's worked well.

I guess KPO4 is still the preferred method. I didn't expect I was the only one, but that's ok. Thanks for all your replies!

[m2434]

What else do you have in your system? The problem I see in a reef tank is that phosphate can inhibit coral calcification even at very low levels.

[Flint&Eric]

you're should dose directly into the algae filter to allow better "absorbtion". the minimal and temporary amount shouldnt effect the corals imo. when po4 is dosed it is because po4 is the limiting factor so the a raise from .o1 to .o5 should be ok.

are there any studies to show at what po4 level that can occur? could be a good guideline for those doing this...?

[Snowboarda42]

+1 on the Food=phosphate

I'd be happy if all my chaeto died off due to lack of nutrients

[Randy Holmes-Farley]

I would second dosing of iron long before I'd try dosing phosphate, unless it was a tank that literally did not get any fish food.

Seachem Flourish Iron is a fine way to go. The ferrous gluconate in it is, IMO, about perfect. I have used it, but now buy it at a local drug store (not much cheaper, but I'm sure of the concentration). Many people growing macroalgae have seen immediate benefits from dosing iron, including the owner of Reef Central.

There is no need to measure iron when dosing it.

This article has more:

First Iron Article: Macroalgae and Dosing Recommendations
http://www.advancedaquarist.com/issues/aug2002/chem.htm

and

Second Iron Article: Iron: A Look at Organisms Other than Macroalgae
http://www.advancedaquarist.com/issues/oct2002/chem.htm

[Red Firefish]

Originally posted by m2434
What else do you have in your system? The problem I see in a reef tank is that phosphate can inhibit coral calcification even at very low levels.

I keep mostly stony corals in the reef tank. SPS corals are domninant, but I also keep several LPS and a few soft corals (mostly zoanthids). The plant tank is not intended just as nutrient export, but as an aesthetically nice display that works in synergy with the reef. There is a healthy amount of calcification in the reef display despite my phosphate additions to the plant tank.

you're should dose directly into the algae filter to allow better "absorbtion". the minimal and temporary amount shouldnt effect the corals imo.

I dose the KPO4 into the refugium as you suggest, and with the pumps off for about 30 min. The plant tank (approx. 15% total system volume) spikes to 0.3 phosphate when I dose with KPO4. This amount, spread over the entire system, tests at 0.03 (Salifert) after 60 minutes mixing, and 0.00 the next day.

I would second dosing of iron long before I'd try dosing phosphate...

Mr. Holmes-Farley, thank you very much for taking the time to weigh in.

The articles on Iron were exciting and informative, and I will begin experimenting with Flourish Iron immediately. I am particularly interested to see how it affects the cyanobacteria within the reef display. As I mentioned in the plant forum, I have noticed that when I forget to dose phosphate for a week or so, cyanobacteria begins to grow in the sand. I have assumed that this was due to phosphate limitation, while nitrogen and carbon were still available at testable levels. Perhaps iron will produce some noticeable change as well.

I am curious- you mention in the first article that iron likely precipitates out of solution if overdosed; would you suspect any potential detriment from allowing this precipitate to accumulate through chronic dosing?

Also, congratulations of winning MASNA hobbyist of the year. You received quite an ovation from those of us at MACNA in Pittsburgh. Thanks for your help!

[Randy Holmes-Farley]

Interesting that you observe cyano when not dosing phosphate. I can't really think why that would be relative to nutrient limitation in other organisms.

Also, congratulations of winning MASNA hobbyist of the year.

Thanks!

[Flint&Eric]

redfirefish, glad to hear it has worked out for you. the cyano popping up does sound strange though. are also adding any type of carbon source the cyano could be utilizing?

congrats on hobbyist of the year. i didnt even know there was such a thing