# Can a second filter be causing more nitrates?



## Sarpijk (9 Feb 2021)

Hi guys, lately I have been dealing with a slight bba problem in my 100 litre low tech. It's been running two years now and so far I had no major problems with BBA.

I realised that two months ago I added a second canister filter to add more flow. I had the filter lying around and thought I should put it to good use.

Is it possible the extra filtration be causing higher nitrates compared to having just one filter?


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## dw1305 (9 Feb 2021)

Hi all, 


Sarpijk said:


> Is it possible the extra filtration be causing higher nitrates compared to having just one filter?


Theoretically it could, but in practical terms almost certainly not.  The increased NO3 scenarios would be:

If your first filter was oxygen depleted you could have a situation where nitrification was limited by oxygen supply and not all the NH3/NH4+ (and/or NO2-) would have been oxidised to NO3-.
If the biofilm was really thick in the first filter you may have had anaerobic denitrification of NO3- occurring. The addition of the second filter has increased the gas exchange surface area and that anaerobic denitrification has ceased.
I think they are both fairly unlikely scenarios. 


Sarpijk said:


> I have been dealing with a slight bba problem in my 100 litre low tech. It's been running two years now and so far I had no major problems with BBA.
> 
> I realised that two months ago I added a second canister filter to add more flow.


We don't know <"what sustains BBA">, but I'm pretty sure that it isn't directly related to NO3 levels. 

cheers Darrel


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## Wookii (9 Feb 2021)

Sarpijk said:


> Hi guys, lately I have been dealing with a slight bba problem in my 100 litre low tech. It's been running two years now and so far I had no major problems with BBA.
> 
> I realised that two months ago I added a second canister filter to add more flow. I had the filter lying around and thought I should put it to good use.
> 
> Is it possible the extra filtration be causing higher nitrates compared to having just one filter?



I guess its technically possible that slightly more ammonia could be reaching the biological filter media and being converted to nitrate before the plants have chance to absorb the ammonia directly.

However, one thing that has largely been proven is that the nitrates aren't causing your BBA. The jury is mostly still out on the exact causes of BBA, but a common anecdotally noted causality is an increase in organics in the water column - and this has been my experience also in my high tech tanks. Generally ensuring detritus removal, clean filters and decent water changes help keep the organics lower.

Also ensuring good surface movement in a low tech to maximise DO and (and also atmospheric CO2 equilibrium), may help. In my low tech tank, I have the filter outlet pointed at the surface, so it actually breaks the surface to help with gas exchange.

Once that is sorted, some misting of the BBA with Excel (with the filter off for 15 minutes) will speed up its demise considerably. I'd also recommend a healthy population of snails and shrimp. In my low tech I've managed, so far, to not see a single occurrence of any type of algae at all. That is something of a miracle for my tanks, and I'm fairly convinced the main contributor is the population of ramshorns, nerites and shrimp pounce 'cat-like' on any microscopic algal growth before it ever has chance to become visible in the naturally slower growth rates of a low tech tank.

EDIT: @dw1305 beat me to the punch lol


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## dw1305 (9 Feb 2021)

Hi all,


Wookii said:


> Also ensuring good surface movement in a low tech to maximise DO and (and also atmospheric CO2 equilibrium), may help.


I'm not sure about this, I've noticed that high flow tanks (<"mainly on PlanetCatfish">) often have "white water" and lots of BBA.


Wookii said:


> I'd also recommend a healthy population of snails and shrimp. In my low tech I've managed, so far, to not see a single occurrence of any type of algae at all. That is something of a miracle for my tanks, and I'm fairly convinced the main contributor is the population of ramshorns, nerites and shrimp pounce 'cat-like' on any microscopic algal growth before it ever has chance to become visible in the naturally slower growth rates of a low tech tank.


Same for me, I'm pretty sure it is invertebrate grazing that makes the difference.

cheers Darrel


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## Wookii (9 Feb 2021)

dw1305 said:


> Hi all,
> 
> I'm not sure about this, I've noticed that high flow tanks (<"mainly on PlanetCatfish">) often have "white water" and lots of BBA.



I was meaning more that the higher DO should help reduce organics Darrel, rather than reduce BBA directly per-se, but I do think higher DO level are beneficial in general for algal prevention. Not sure what is going on in those catfish stream tanks - possibly too many variables to be sure?

I have had BBA grow in high flow and very low flow areas, in areas both brightly lit, and almost completely shaded. It's also grown for me in areas of very low CO2, and others in areas of the tank where the CO2 must be at the highest level. My only anecdotal link to its appearance is a slacking off of maintenance, and its disappearance by upping maintenance.

In a high tech I (presumably) get DO saturation from the plants (if extreme pearling on all plants is evidence enough), but I don't see that in my low tech, presumably due to the much lower light and CO2 levels, so promoting surface gas exchange is the only way I know of maximising DO and CO2 (other than a trickle filter based sump, and the controversial electrolysis devices).


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## dw1305 (9 Feb 2021)

Hi all, 


Wookii said:


> I was meaning more that the higher DO should help reduce organics


It should do, if you have enough oxygen then all the <"potential oxidisable material will consumed">. 


> ........The extended aeration system is one of the modifications of the activated sludge process. It is a complete mixed system that provides biological treatment for the removal of biodegradable organic waste under aerobic conditions. Air may be supplied by mechanical or diffused aeration means. The raw sewage directly flows into the aerobic digestion chamber where all the solids are digested by aerobic bacteria. This is possible because the sewage is aerated for a minimum of 24 h, giving vastly increased time for almost complete digestion of all solids.





Wookii said:


> get DO saturation from the plants (if extreme pearling on all plants is evidence enough)


Definitely shows oxygen saturation. 


Wookii said:


> but I don't see that in my low tech, presumably due to the much lower light and CO2 levels, so promoting surface gas exchange is the only way I know of maximising DO and CO2


That is the approach I take as well.

cheers Darrel


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## Sarpijk (9 Feb 2021)

Thanks for the input. My main goal was to decide if I should remove the second filter. Something I should mention is that lately I started seeing a surface film although my plants grow fine. Moreover another change I made was removing a great number of ramshorn snails- still have lots to compensate. The main problem with bba is on Bucephalandra leaves especially the ones in front of the water flow. Also I have a fan shrimp which gets covered in BBA but will soon shed its skin so that's no big deal.


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## dw1305 (9 Feb 2021)

Hi all,


Sarpijk said:


> I started seeing a surface film..............I made was removing a great number of ramshorn snails- still have lots to compensate. The main problem with bba is on Bucephalandra leaves especially the ones in front of the water flow. Also I have a fan shrimp which gets covered in BBA but will soon shed its skin


Both the BBA and the <"surface scum"> may relate to the removal of the snails. The fan shrimp is interesting I've noticed that I tend to get <"BBA in high flow areas and sponges">, where I assume that I don't have <"any snail grazing">.

This is Marcel's @zozo 's "Punk snail"






cheers Darrel


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## Sarpijk (9 Feb 2021)

What is very peculiar is that whenever I had a surface protein film was because the filters needed to be cleaned. I just opened one of the filters and there was hardly any mulm in it! I still cannot understand the reason for high organics. Could it be because it is a two year old dirted tank?


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## ceg4048 (10 Feb 2021)

> Wookii said:
> get DO saturation from the plants (if extreme pearling on all plants is evidence enough)





dw1305 said:


> Definitely shows oxygen saturation.



Actually, I believe it's a bit more complicated than that. Heavy pearling _can _be an indication of DO saturation, but it's not necessarily always the case. There is a rate at which O2 can dissolve in water, dependent, like all gasses, on temperature, pressure and salinity.
If the rate of O2 production/ejection by the leaf exceeds the solubility rate of the gas then bubbles will form. So it's entirely possible for the water to not be saturated, but that the gas exits the leaf at a rate at which the water is unable to absorb as quickly, so the gas escapes as bubbles.
O2 has very poor solubility in water, so the saturation threshold is low but the solubility rate is also very low.

Cheers,


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## Sarpijk (13 Feb 2021)

I may have found a possible cause for the BBA which I haven't mentioned that it has mainly occured in the front part of the tank.

Compared to previously the flow was massively restricted despite the two external filters. In my search for turbulent flow I invested in two third party outflow nozzles (left) but they never performed as expected and only realised that yesterday when I removed one of the filters and switched the outflow nozzle with the generic one made by Fluval ( right)

I believe this improved flow will remove the debris from the substrate in the front as it did few months back when I had no visible BBA.

The removal of snails was drastic but I still seem to have hundreds.


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## Mark Nicholls (13 Feb 2021)

Assuming that your existing filter is working to full capacity and is the correct size for your tank, adding an extra filter will NOT increase the bacteria! 
The bacterial population is limited by the amount of available Ammonia and Nitrite. So... 
Unless you add more Ammonia, it's impossible to increase the amount of bacteria HOWEVER MANY filters are used!!!


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## Zeus. (13 Feb 2021)

late to the party 



Sarpijk said:


> is it possible the extra filtration be causing higher nitrates compared to having just one filter?



I would say it 'might' increase the peak [NO3] if you was doing an ammonium or urea based fertilizer, if the tank was getting good surface agitation. As two filters with a good O2 supply would help speed the conversion of the base salt to NO3.
Would it make any 'real' difference  IMO NO

If dosing a KNO3 based fert -No


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