Does higher KH favour higher algae?

[bclee]

Following the discussion from another thread...

My observation is that higher carbonate level in water seemed to favor certain algae species, like BBA and the fuzzy green algae.

I have read that red algae species, especially the marine species (not too sure about FW ones), are able to assimilate carbonates as their carbon source. I am wondering if this reduces the effectiveness of using high CO2 to control these algae in carbonate rich water (KH >10 or even much higher).

I wonder if anyone of you who have really research into this or have relevant experience to support or refute this.

BC

[PeterGwee]

BC, seems that you believe it is so that high KH does help BBA and fuzzy algae grow? Why don't you lower the KH of your current tank by doing more changes and compare if the algae spieces still bug your tank when the CO2 is high. I'll tell you if the CO2 is good, what you need to work on is just the nutrients. There are issues with NO3 kits that most folks are using and believing them makes things worst. I did believe those kits at some point but got loads of algae (BBA, green fuzzy ones, hairy ones, spotty ones..you name it.). I remove them weekly and they came back instantly! Now, I don't have any..... Somewhere things went out of whack for your tank. You need to nail that bugger...

Regards
Peter Gwee

[bclee]

The problem is that the source of KH is the Onyx substrate. It keeps the KH up unless I am changing water every day . It is not so easy to lower the KH.

The other variable that I may not be able to measure or quantify is organic carbon. Some algae have also capability to utilise organic carbon. This is one thing that I cannot rule out.

Why not you raise your KH to help me verify this? (Just joking... :P )

BC

[bclee]

BTW, I dose traces, a little Ca & Mg, NO3, PO4 & K 3 times a week... very much like Tom Barr's estimative index.

I have not touch my test kits for months, except for KH/GH.

BC

[PeterGwee]

How much did you dose? If your CO2 and light is good and plant biomass is heavy, nutrient removal can be pretty high and that is when things can get bad when nutrients run out. Did you see plant growth slowing down near the end of the week? Increase in algae growth as the week ends?

Regards
Peter Gwee

[bclee]

Weekly it is about 30+ppm of K, 15ppm of NO3 and 3~5ppm of PO4.

BC

[PeterGwee]

Mmmm..I still think is the CO2 after you name the nutrients. Why don't you write to Tom..He'll give you a better answer.
Personally, I'll remove as much algae as I can and add back plants if the prunning is way excessive. Clean the filter to clear out new spores. Do 50-70% water changes. Check the CO2 at least 2x both am and pm readings. Dose back nutrients 2-3x per week to prevent things from running out and doing weekly 50% to prevent things from building up. Keep up on the cleaning and things should improve and algae gone in about 1-3 weeks generally.

Regards
Peter Gwee

[geoffrey]

I doubt BC will get his CO2 wrong. I suspect he has been pushing his CO2 pretty high, given the fact that his KH is rising. Some form of carbonate in his substrate is dissolving as a result of his high CO2.

BC, have you try pushing your NO3 higher by increments of 5ppm to see if it helps?

I have a KH of 7. Is that high? Occasionally those pesky BBA and fuzzy bushes do come back, but only when circulation is inhibited by heavy growth, otherwise it's ok.

[juggler]

BC: were there any changes in the dosing regiment before the outbreak of the BBA?

In one tank, I once increased K from 10ppm to 15ppm and I got sudden growth as well as outbreak of Brush Algae.

[Plantbrain]

algae will grow well at higher KH's just like the plants pretty much, both use CO2. Some plants like most all FW algae can use HCO3.
But both use CO2 ultimately.

There are a few ways to do this, HCO3 uptake(some Myriophyllum) and indirect HCO3 usage(eg Hydrilla).

Some algae do it directly with CO2 in the water and have small Carbon needs. Also, algae are in a completely different habiat than plants.
They are both in the water, but due to their size differences, the habitat is radically changed.

Plants/algae will tend to have higher photosynthetic rates at higher HCO3 levels, since if the CO2 runs out during intense photosynthesis, they can use the HCO3 next.

Basically there's more total carbon in the harder waters.

You can see this on growth curves, the Bowes, Van, Haller paper showns this in figure 4.

So plants actually prefer hard water, not soft! At least in terms of Carbon which is the most often limiting nutrient.

Also, the level of saturation in aquatic plants is roughly 10X higher than air. So an air level of 3-5ppm is translated to about 30ppm CO2, almost 2x the amount recommened in the past by Paul Sears, Dupla and other folks.

The CO2 compensation point is important in optimzing maximum growth just as is the light saturation/compensation point.

Regards,
Tom Barr

[bclee]

Tom, what is the genus/species name of the BBA we commonly find in our tanks?

The other difference from my current setup to the previous one is the peat in the substrate. I have added about 1/2" think of peat under the Onyx. (I thought that the peat might counter the effects onyx in terms of rising KH and I was wrong! ) I am suspecting that I am also having more organic carbon in the water. Will this make a difference to algae growth?

BC

[bclee]

[quote:cee622de43="juggler"]BC: were there any changes in the dosing regiment before the outbreak of the BBA?

In one tank, I once increased K from 10ppm to 15ppm and I got sudden growth as well as outbreak of Brush Algae.[/quote:cee622de43]

I have added more NO3 and PO4 compared to what I previously added. I have found that NO3 uptake was slightly more than previously with lower KH. (Well, Tom's explanation did match up with my experience.)

I have varied K from 0ppm (excluding that from KNO3) to 40ppm. I find it might have been slightly better with higher K level.

BC