# BGA and Water Flow



## Mnemia (Nov 23, 2004)

I've posted about this here before, and I've read some other posts about this, but I thought I'd ask. I keep having a persistent problem with cyanobacteria that I just can't seem to keep down. I KNOW that I'm dosing enough KNO3 as I'm adding a huge amount of it and the levels test consistently sufficient (I'm not just blindly trusting the test kit; it's calibrated and it works properly against a known sample). I'm trying to have at least 10-15 ppm of nitrate at any time, and I believe that I'm being consistent about this. My CO2 is also plenty high (cranked until fish started gasping and then pulled back slightly). The plants are growing extremely rapidly and pearling continually. In order to try to eliminate the BGA I've been especially vigilant about keeping the substrate/plants spotless for the last few months. I've been cleaning it out twice a week and doing a large (50-60%) water change weekly. I know the advice is always to add more CO2, but I've already done that to the point that it's stressing my fish.

I've tried everything I can think of short of using antibiotics...including a 4 day blackout. This killed most of the BGA but stressed my stem plants and it came back very soon after. I don't see much point in using antibiotics if I can't figure out why it's growing as it will just come back, maybe in a drug resistant form.

I believe the problem is too little water flow, maybe preventing the CO2 from getting throughout the tank. I've got some huge crypts and anubias barteri var. nana on a big piece of driftwood and the BGA mostly forms on the substrate and stem plants around the base of the wood, in little stagnant pockets. For this reason, I've come to the conclusion that the only possible issue remaining is that my little HOB filter just doesn't cut it anymore with those big plants blocking the water flow from it (although this is only a 20 high).

This is driving me crazy, and I want to figure out how to solve it. Do you think it would be helpful for me to replace the HOB filter with a canister to get more flow/circulation? I'm willing to spend the cash, but I don't want to unless people agree that this is the most likely cause of my problem. If you feel this would helpful, how big of a canister filter should I be looking at for a 20 high that seems to have a problem with inadequate flow?

Thanks in advance for the help.


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## Blazerfrs (Feb 3, 2006)

I don't see the need to replace the filter if all you need is more circulation. If I were you I'd probably add a small power head- maybe an AC20 or equivilent. See how the cyano reacts to circulation. 

I did have BGA awhile ago that I treated with antibiotics... it worked well for me, but is def. a last resort type move. 
Good luck


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## yellowfish (Feb 2, 2006)

I had BGA, it got so bad that it killed all the algae in the tank. What I did, I use four day antibiotics, the dose was high I think 250mg for every 10 gal. It worked with the use of KNO3, but it killed my filter and to cycle the tank some what, but I was not running any co2 in the tank of only crypts. I think the cause of my out break was the lack of a fish load and no ferts. Water flow is not your Problem most of the time you see it is on the out flow from the filter(red type alot). Good Luck


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## JaySilverman (Jun 19, 2005)

IMO flo is extreamly important in combating algae. Since I upgraded the flow in my tank algae has died down significantly.


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## BigChuckP (Oct 8, 2005)

I have always been told you should not have surface agitation when you are injecting co2 and I believe all hob filters do disturb the surface so your co2 is dissipating (maybe wrong word) out of the tank...do you ever test your ph?


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## Mnemia (Nov 23, 2004)

BigChuckP said:


> I have always been told you should not have surface agitation when you are injecting co2 and I believe all hob filters do disturb the surface so your co2 is dissipating (maybe wrong word) out of the tank...do you ever test your ph?


Of course. My pH is stable at ~6.4 with a KH of 2. According to the chart, this translates to about 36 ppm of CO2. I don't really trust the chart or test kits, but I trust the fact that my fish start to look stressed if I increase the CO2 any higher, and the fact that I don't have any other algae like BBA with this much CO2. Anyway, the surface agitation from the HOB filter shouldn't really matter, from what I understand, with pressurized CO2 since you just can just increase the rate of injection to compensate for any CO2 lost to the surface movement.

I'm more concerned with the fact that I seem to have stagnant "dead spots" in my tank where the water doesn't really circulate (I can tell because if I stir up mulm/substrate there then it doesn't move much at all). This is where the BGA builds up rapidly, around the big barrier-like piece of driftwood that's in my tank.

I've thought about this some more and I'm starting to lean towards just getting a more powerful canister filter to move the water quite a bit more. In any case I currently have an empty 10 gallon tank that I'd like an excuse to press into service. I might just move the HOB filter to that tank, so it's not like it would go unused if I upgraded on the 20.


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## plantbrain (Jan 23, 2004)

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## Mnemia (Nov 23, 2004)

Tom, 
Thanks for the help.

The blackout procedure I followed was 4 days with the tank covered completely, preceded and followed by a filter cleanout and large water change. No CO2 during the blackout.

I've been dosing an even larger amount of KNO3 than before (I wasn't relying on test kits - at all, and I am actually dosing more than you suggest above). I'm still getting some BGA on the parts of my substrate that are uncovered and in stagnant pockets. I don't think it's actually growing any more, so I can only assume that you are correct and I somehow let the nitrate level bottom out. 

I also discovered by experimenting with it that spot treatment with Excel will kill the BGA on contact. I used a small syringe and squirted it right onto the pockets, and it turned gray and then died - the die off was only in the areas where I used the Excel. Of course, this isn't practical as a way to kill a large amount of it, but I think I'll keep it in mind if I see small bits of it show up on plants, etc in the future.

Thanks for the recommendation on the filter upgrade...I will definitely get some more flow after this episode.


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## plantbrain (Jan 23, 2004)

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## Faruk Gençöz (Nov 4, 2005)

I would use a school of corydoras in the tank. Before I put them in to the tank I would remove BGA from the substrate as much as possible and do a major water change along with the filter media cleaning. Corydoras may not help every time but if you believe that it is the flow you need, a school of corydoras provides a lot of it on the substrate.


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## plantbrain (Jan 23, 2004)

edit


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## Mnemia (Nov 23, 2004)

This is in fact a relatively old substrate (2 years), so I'm sure that's part of the problem I've had. I've been trying to make sure I get things extra clean and deeply cleaning the substrate by doing a big water change every two days. I'm also keeping up on the KNO3, and doing the daily spot treatment with Excel that I mentioned on the hard to get to places like the crannies at the base of my driftwood. New filter will arrive Monday as well, and once I'm convinced everything is nice and clean on the substrate I will replant stem plants.

This all seems to be having an effect as the BGA is definitely slowly dying off (or rather, it isn't growing and the cleaning and the Excel are killing it). No antibiotics needed this time!


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## banderbe (Nov 17, 2005)

Mnemia said:


> Of course. My pH is stable at ~6.4 with a KH of 2. According to the chart, this translates to about 36 ppm of CO2


No, your CO2 according to those values is around 24 ppm.

As you are probably aware, those charts are based on the formula:

3*KH*(10^(7-pH))

So, yours is: 3*2*(10^0.6) = 23.886

Have you tested your pH with another brand of kit to verify accuracy? What about checking with your city to get a water report to verify KH?


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## Mnemia (Nov 23, 2004)

banderbe said:


> No, your CO2 according to those values is around 24 ppm.
> 
> As you are probably aware, those charts are based on the formula:
> 
> ...


Sorry, I meant to type 26 ppm (the number that one of the online calculators for CO2 gave me). Obviously that number was a little off. But, I'm not relying on a test kit to tell me how much CO2 I have, as I said before. I'm relying on the fact that my plants are pearling heavily and that my fish are stressed if I turn it up any more (as I said earlier).

I also question the accuracy of the CO2 chart for testing tank water, given the number of other variables possibly involved (such as acids or bases other than carbonic acid in the water or other buffers besides bicarbonates). I also don't think that cheap test kits are able to give accurate enough readings for KH and pH for us to draw these precise conclusions about the CO2 level in our tanks. I do know that my KH reading ROUGHLY agrees with what my town's water quality report says, but I don't just blindly trust it. Those simplistic CO2 equations are in my opinion only a very rough guide as to the amount of CO2 actually present. I would be a lot more concerned if my pH wasn't so different from the pH of my tap water or something. Actually I think that my KH is less than 2, as it tests as 1.5 if I use the method where you double the amount of tested water and then use twice as many drops to titrate it, with each drop counting as 0.5 dKH rather 1 dKH. This is more in line with what the city says, which is 30 ppm. So likely my CO2 level is higher than 24 ppm anyway.

In any case, I don't have problems with other algae like BBA or GSA, which I think I would if my CO2 was too low. I believe that Tom is correct and the real cause of my BGA was primarily letting nitrates get to low combined with low water flow combined with a buildup of mulm in an old, heavily used substrate. I sucked a huge amount of mulm out of those stagnant pockets a couple days ago, and the BGA hasn't grown back. I think I mostly just need to be more vigilant about deep cleaning the substrate now that it has been in use this long.


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## ChrisP (Nov 29, 2005)

Can I ask when you say add 1/4 teaspoon 2x week thereafter do you mean per 20 gal? Also does it sound right if I were to add 1/4 teaspoon per 20gal after a 50% water change and then again the same amount mid week?



plantbrain said:


> Well, you did something wrong if you read my blackout advice, that much is painly clear. Stop worrying what the test kit says, add more KNO3.
> 3 days will do the blackout, no need for 4.
> 
> Clean well first, you probably are old hat at that routine by now.
> ...


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