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Hardness & algae

Snowstreams

New Member
Joined
4 Nov 2021
Messages
11
Location
Ireland
I haven't had any green algae in my tank since I started it nearly 3 months ago, but I had plenty of brown algae/diatoms. Some bba too I think after I tried DIY co2.
I have lowered the tds in my tank after my last 2 water changes (using ro water) & now I've noticed that the brown algae has all turned green. My newer leaves still have chlorosis though but I'm hoping the green algae is a sign that iron is now available in the water column.
Are there any root fertilisers that can supply a stable iron in moderately hard water?
 

Angus

Member
Joined
29 Aug 2008
Messages
641
Location
Vauxhall, London.
Water hardness has nothing to do with algae.
It is correct that there are many factors. Hardness is not one that warrants attention.
Do you think this is definitely the case? as i feel from growing in hard water i have experienced excessive occurences of BGA and rhodophyta alongside detritus and silting in my tanks, do you feel it is solely because of the 'humic substances' or does bicarbonate availability have a part to play in all this? interested to hear your thoughts ceg.
a fluorescence analysis revealed that the bicarbonate treatment supported effective photosynthesis, while the CO2 treatment led to inefficient photosynthetic activity with a PSII maximum quantum yield as low as 0.31. Conversely, bicarbonate and CO2 treatments gave similar biomass and fatty acid production.
Umetani, I., Janka, E., Sposób, M. et al. Bicarbonate for microalgae cultivation: a case study in a chlorophyte, Tetradesmus wisconsinensis isolated from a Norwegian lake. J Appl Phycol 33, 1341–1352 (2021). https://doi.org/10.1007/s10811-021-02420-4
 

ceg4048

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UKAPS Team
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11 Jul 2007
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Chicago, USA
Do you think this is definitely the case? as i feel from growing in hard water i have experienced excessive occurences of BGA and rhodophyta alongside detritus and silting in my tanks, do you feel it is solely because of the 'humic substances' or does bicarbonate availability have a part to play in all this? interested to hear your thoughts ceg.
Hello Angus,
Yes absolutely. There is no correlation whatsoever between water hardness and algal blooms.
BGA normally indicates either a problem with low levels of nitrate or, as you mention, the buildup of organic waste, which can release ammonia/ammonium into the water column and trigger the blooms. Red algae are usually triggered by poor CO2.

Now, your extract addresses the relationship between the photosynthetic efficiency of a species of algae and bicarbonate, so I'm assuming, when you mention "water hardness", that you are referring to "carbonate hardness (KH)" as opposed to "general hardness (GH)" which are two very different properties.

What we need to realize is that just because an algae is able to metabolize some product in the water column it does not automatically mean that if that product is found in our tanks then an algal bloom will appear. People use this excuse all the time to blame a variety of products in the water column as trigger for algae. The most famous case is the diatom algae, which uses silicates to strengthen it's cell walls. So hobbyists become hysterical about attempting to remove silicates from the water. This never works because the amount of silicates in the water can be practically zero, yet the diatoms will find a way to bloom. The reason is that they are not triggered to bloom simply by the mere presence of silicates. They are triggered by other environmental factors in the tank that may or may not be within our control.

Similarly, BGA and rhodophyta do not really care whether there is a high concentration of carbonate or bicarbonate in the water. They are very small organisms and only require a very small amount of CO3/HCO3 to function. They are not encouraged to bloom simply because of the presence of CO3/HCO3.

The list goes on and on of products that are claimed to be triggers of various algae. Nitrate and phosphate are blamed all the time for various algal blooms, but none of this is true. Fundamentally, we need to keep the tank and filters clean with regular large water changes and we need to feed the plants the proper amount of nutrients based on the configuration of the tank, i.e., low tech or high tech.

By the way, there are plenty of plants that also use CO3/HCO3 as alternate sources of CO2, most famously, Vallis.

Cheers,
 

Angus

Member
Joined
29 Aug 2008
Messages
641
Location
Vauxhall, London.
Yeah sorry i am referring to KH when i say hard water, My vallis is always lovely indeed, we have liquid chalk here.

Rhodophyta induced by poor co2... makes sense i haven't used it in ages, and their other source of carbon is bicarbonates right especially as they are essentially a coralline algae unless i'm mistaken.

Thanks for the in depth reply, loved reading it, so in a non co2 injected tank would you say the existence of bicarbonates could increase algae growth post bloom (as a result of increased build up of decomposing waste) as opposed to a co2 injected tank? if the value's in that study are correct and co2 infact limits microalgal productivity compared to bicarbonates?

i'm very curious is all i'm by no means trying to come to any conclusions myself i'm such a pleb when it comes to science, just trying to draw information out of you ceg... :lol::thumbup:
 
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