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Could floating plants be it?

Brenmuk

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24 Jul 2008
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Peterborough
I have often wondered how plants suppress aglae growth. The theories I have come across so far are

1)Competition for bio available iron in the water column which is usually in short supply
2)Allelopathy - chemicals released by plants that inhibit algae growth (all sorts of organisms can release allelopathic chemicals not just plants).
3)The latest from Ceg4048 is competition for ammonia.

One thing I have found is simply having plants in the aquarium is not enough they have to be growing to suppress algae.
 
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stroud, glos
Brenmuk said:
I have often wondered how plants suppress aglae growth. The theories I have come across so far are

1)Competition for bio available iron in the water column which is usually in short supply
2)Allelopathy - chemicals released by plants that inhibit algae growth (all sorts of organisms can release allelopathic chemicals not just plants).
3)The latest from Ceg4048 is competition for ammonia.

One thing I have found is simply having plants in the aquarium is not enough they have to be growing to suppress algae.

for what my opinion is worth,
i think the iron thing is like nitrates and phosphates in the way they are blamed for causing algae but actually dont, they can possibly make an out break worse if at "high" levels after something else, ie ammonia triggers it.

as for allelopathy, while i think in some cases it may be an influence, more so in low tech, no/low water change tanks. it probably has little or no effect in tanks that have regular/large water changes.
think about all the types of plants ppl have together, if the effect was that great it would be harder to mix all the plants we do.
of course i could totally wrong and in fact it's the key to everything! :D
 

Brenmuk

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Joined
24 Jul 2008
Messages
198
Location
Peterborough
baron von bubba said:
i think the iron thing is like nitrates and phosphates in the way they are blamed for causing algae but actually dont, they can possibly make an out break worse if at "high" levels after something else, ie ammonia triggers it.

as for allelopathy, while i think in some cases it may be an influence, more so in low tech, no/low water change tanks. it probably has little or no effect in tanks that have regular/large water changes.
think about all the types of plants ppl have together, if the effect was that great it would be harder to mix all the plants we do.
of course i could totally wrong and in fact it's the key to everything! :D

I know what you are saying about water changes throwing a spanner in the works for the allelopathy theory (using carbon in filters might also counter this theory as well) and assuming that iron is like all the rest of the major nutrients in that more not less is beneficial then its tricky to see how plants can suppress algae growth. If you accept the idea that algae are low light low nutrients scavengers then why don't they grow along side plants in a tank that is for example having ferts added - you would think there is enough ferts for both algae and plants to grow side by side.
This leaves 3rd theory -competition for ammonia - but surely you could argue that an efficient filter would be able to remove ammonia? Also ammonia is constantly being produced by fish etc why isn't there a constant growth of algae?

[Edit] I've just googled this question and found some good articles by Tom Barr who makes a convincing arguement for ammonia as being the trigger for algae growth. I'm sure i've googled this before i suppose it goes to show the effect of putting certain phrases into google!
 
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Brenmuk said:
I know what you are saying about water changes throwing a spanner in the works for the allelopathy theory (using carbon in filters might also counter this theory as well) and assuming that iron is like all the rest of the major nutrients in that more not less is beneficial then its tricky to see how plants can suppress algae growth. If you accept the idea that algae are low light low nutrients scavengers then why don't they grow along side plants in a tank that is for example having ferts added - you would think there is enough ferts for both algae and plants to grow side by side.
This leaves 3rd theory -competition for ammonia - but surely you could argue that an efficient filter would be able to remove ammonia? Also ammonia is constantly being produced by fish etc why isn't there a constant growth of algae?

this is the way that i understand it......
the plants will be working with the bacteria in ridding the tank of ammonia and the bacteria colony will only grow as big as it needs to, if plant growth halts/slows for any reason, ammonia can rise before the bacteria colony grows suitably large enough to deal with it.
in a higher light situation this can happen pretty quick, i think a lower light tank is more forgiving.

i'm sure someone will put me right or at least put it more eloquently.
 

JamesC

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3 Jul 2007
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Bexley, Kent
I don't think it is quite so simple as saying ammonia triggers algae. Have too much then yes it does cause problems but many people add ammonium to their tanks daily. Those that add TPN+ actually add fairly large amounts of ammonium and I myself add urea daily. Nearly all commercial products that add N have that N in ammonium or urea compounds alongside nitrates. Perhaps the plants gulp it up so fast?

James
 

ceg4048

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Chicago, USA
As James indicates, it's not as simple as just having ammonia. The ammonia production rate and removal is a factor, lighting is a factor, temperature is a factor, CO2 and there may be other contributory factors such as O2 levels. Algae flowers from spores. The sensing mechanism of the spores is still not fully understood, we only have high correlation between their appearance and the known factors listed above. It is not enough to simply have plants in the tank. There is a relationship between the plants and the resident bacterial population within the water/filter/sediment. I would say without a shadow of a doubt light is THE single biggest factor. When the lighting is extremely high you don't need very much of any of the other factors to trigger blooms. As the light energy is lowered however these other factors become more influential. When the lighting is zero the other factors again become irrelevant and no algae is triggered. One can then hold the lighting constant and vary the other factors to get different combinations to trigger the blooms.

Healthy plants increase ammonia removal rate by direct ammonia uptake. They also grow more quickly and deter algae from forming on their surface. They also oxygenate the water and sediment thereby increasing the resident bacterial population. This magnifies the nitrification rate on all levels further increasing the ammonia removal rate. Of course you need a high plant mass to have a significant impact on the removal rate, and of course you need a mature tank in order to have a sufficient bacterial biomass to have a significant impact on ammonia removal rate. That's why new tanks are at greatest risk as they usually lack one or the other. When the tank is then illuminated with high lighting this exacerbates the problems. If there is severe imbalance biomass, then even low tech tanks are susceptible to blooms.

Unhealthy plants are a liability in a tank because their cells die and decay which amplifies the ammonia production rate and does nothing to help the removal rate. Algal armies then colonies and attach to their surface to feed on the nutrients erupting from the dead and dying cells. This is why the blooms attack the plants directly. Unhealthy plants support less bacteria so that bacterial nitrification is also attenuated. Bad combination basically.

Until further data is available I've drawn the tentative conclusion from Barr's explanations that the ammonia laced nutrient products (in some cases) either are not dosed at a high enough NH4 concentration level to significantly disrupt the production/removal equation, or, if dosed regularly and are at high levels, will simply cause a sufficient rise in the itinerant bacterial population which then oxidize the ammonia to nitrate in addition to simple plant accelerated uptake of NH4. Urea addition is addressed by the urease which is in abundant supply in the tank and which acts very quickly.

Cheers,
 
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