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Re: FeSO4

>> It's unlikely you can beat diatoms with Si removers,
> they can live in very
>> pure water and are often found in such locations.
> Is it safe to generalize about all diatom species? Why
> do reef aquarists use Silicate removers to control
> diatoms?

With FW yes, SW is another issue, coastal regions are unlikely to be Si
limited, open central gyre's far from land certain regions may become Si
I'm not so sure RO water for reef tanks is really that good/great, solves
what they claim etc. SW algae are different in some respects but the ocean
is a very big place with lots of species.

SW aquarist also seem to really hate water changes a great deal. I've seen
many spend 500$ trying to save 50$ in water changes.

I don't think many reef folks will try _adding Si_ to their tanks.

I on the other hand do nutty stuff like that.

I don't care that much and cleaning algae from a macro algae tank is
different mind you, but it's all the same old after awhile.

But using RO and then using w/ or w/o the Si addition, would give some
indication of whether Si is really the culprit or not.

I think most are too chicken to try it and have lots of $ in livestock as
well so they have other motivations not to fiddle with their tank.

PO4 does not appear to be the big hairy deal, but I also have macro algae/a
refugium for a tank.

Reef only tanks, unlike planted marine tanks, often use a plant refugium
full of macro algae to filter the water. This is similar to a planted tank
being used to filter a larger critter/fish tank.

I'm still playing with PO4 and NO3 with the SW.

NO3/PO4 doesn't have too much response.

Traces seem to at higher levels. I need to work on this more.

Si is something I have not messed with since it's non limiting in FW.
But I don't use RO in my Marine tank, I have no problems unless I overdose
something like the traces, 70% tap water changes have only a positive

Many super soft water regions have unusual diatoms.
>> PO4 has been shown here and numerous other research
> studies that it does not
>> cause algae outbreaks __when growing plants__ are
> present.
> Can we assume the reason is that the plants are
> depriving the algae of their share?

No, they both have access to 1.0ppm of PO4 either way floating around in the
water column, there's no limitation occurring.

 If so, what
> happens when the Phosphate levels exceed the plant
> requirements...won't the algae now have access to the
> excess?

No. But you can add so much of some nutrients that it destablizes the
Plant's do not need 1.0ppm of PO4 to grow well, they will dom fine at
.2-.3ppm, but that amount will run out in a day unless you add more(If you
have a CO2 enriched tank with all the other parameters set correctly).

 Why do we aim for a Phosphate content of
> 0.4-1ppm and not more? After all, all I was aiming at
> was to get the Phosphate from 3-4ppm down to this
> level. 

More is simply wasteful. Above and beyond etc. You can do the same with
Traces and K. Have enough for the plants to eat for a a few days(3-7
depending on the tank/lighting etc)

NO3 and CO2 are the ones that cause the most grief if they get too far
outside their ranges.
> Appr. 10 years ago I cleared the pond of a green hair
> (?) algae problem by reducing the pH of the water
> using Phosphoric acid. Shortly after all the plants
> were covered in a brown dust, which at first I thought
> was mulm churned up by the fish, but then, under the
> scope, saw they were diatoms . Phosphate levels at
> that time were v. high due to the acid. Coincidence? I
> remember that a couple of water changes (phosphate
> free then) solved the problem.

If the pond was PO4 limited, adding PO4 will generally induce a bloom, if
the pond has a good amount of plants, the plants should bloom, start growing
like mad etc, there should be little bloom at all.

Plants in ponds etc, out compete algae primarily by light competition.
> Nitrate problems are very low. I have to add it daily
> to try to keep it in range. I don't think that's the
> problem. BTW Can't algae utilise disolved short
> chained organics?

Sure, you can keep some algae alive without light even using acetate.
This is very useful for plant biochemist and others studying their photo
>> Adding PO4/Fe etc to a densely planted lake/pond/tank
> will
>> cause algae, the plants will grow more, but if
> there's around 50% coverage
>> on the lake, maybe more on smaller systems, you
> should not see algae
>> increase. 
> Sorry, can't understand this.

If the lake has 30-50% of more plant coverage, the lake will not bloom with
nutrient inputs(within reason).

We have lakes like this where they have relatively high NP levels and clear
water. Remove the plants ("Let's get rid of these vile weeds that choke my
boat propellers"), you get algae. Then they whine about the murky pea soup
they just created by killing off the plants with herbicides etc.

Adding PO4 helped many lakes grow more plants and become more choked with
weeds, but no algae.

Most of the studies on PO4 did not deal with tropical/subtropical shallow
lakes nor plant infested waters.

These are much different lake systems and much more so like our planted
>> So what happens when you uproot a plant? What
> happens to all that mulm?
> Why have a mulm problem? I use a scissors to cut off
> the roots before leaving the substrate, just leaving a
> couple of inches on the plant. The rest stay in the
> substrate.

Stumps a plenty:)
I can't do that:) They get yanked, only fresh tops get replanted, these have
far less algae, healthier etc.

>> Plants will take in PO4 rapidly from the water
> column, this can be measured.
> All types of plants? Will a tank composed of 90%
> Anubias, moss, ferns, echinodorus and crypts utilise
> alot of Phosphates rapidly?

Sure. Bolbitus loves PO4, Anubias, swords? Hehe. Dang, those get too big too
fast for any tanks of mine. Crypts love PO4. Gobble gobble.

If you have one watt per gallon, no CO2 etc, will you be able to see the
uptake well per days? No.
But if you raise the lighting up to 2-3w/gal, add CO2 now you actually have
removed the light limitation and the carbon limitation on the plants(Algae
have no problem using KH(bicarbonate, HCO3) for a carbon source, doesn't
slow them down, then you will be able to see changes in PO4 uptake rates etc
per day etc.
Plants use up far more PO4, NO3, etc than algae will in the same tank if you
prune etc and do the routines to keep the plants healthy and growing(dosing,
CO2, water changes etc).

>> Resuspension of that PO4/Fe from a reductive
> substrate will cause a bloom if
>> the water is PO4 or Fe limited which is likely the
> case if it cleared the
>> problem up over the long term
> How can the phosphate be resuspended if it is combined
> to the iron?

It is reduced in the substrate where it ends up. Roots are suppose to get
the PO4 remember? They do this a number of ways but pumping H+'s out to the
surrounding area is the main way they obtain most ions.

It takes time for the soupy water with the PO4 and Fe to precipitate out.
Your tank did not clear in an hour etc.

 And even if it can, won't it recombine
> and precipitate? 

Yes and it will happen, but it takes time for that to occur and the algae
get well fed.
>And even if some of the iron has been
> used by the plants and there is a phosphate excess,
> why not just add more Ferrous sulphate?
> How can it be Fe limited? - I added not removed the
> iron. I also add chelated iron.

Well it will not be Fe limited if you add it to the water column.
I think you will have an impossible time Fe limiting a FW algae with plants
present or with an iron rich substrate.
> So, are you suggesting that a high PO4 level can be a
> cause of a bloom? - in the right circumstances?

> If so would'nt that partially explain why the Ferrous
> sulphate worked. ; )

Yes, in your case.

Many folks have used this same method to clear up lakes with phytoplankton.
But, that PO4 and Fe go somewhere in the lake, it's not removal, just
storage. Resuspension can and does occur in some lakes. You have not removed
it, just put in in the gravel.

If it works for your tank, use it.
There are a number of commercial and research articles on it on the web I
believe. We discussed using it in a class on Limnology in depth as it
applied to shallow planted lakes.

Tom Barr
> Regards
> Stephan