# Floater cover...



## ajadcock (16 Oct 2015)

Hi all,

I have a question about my floater coverage:






Because of the almost total coverage I have very little surface agitation, so reduced gas exchange.
My question is do you think would the floaters release enough o2 into the water to not worry about it?
Oh and its posted in here as its a low tech 
Thanks! 

Adam

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## Tim Harrison (18 Oct 2015)

I think that you need agitation to get the dissolved O2 in to the rest of the water column, otherwise I reckon a lot will be trapped just under the surface and eventually lost to the atmosphere.
_Lemna minor_ isn't my favourite floater there are many others more suitable and more able to withstand agitation, which is perhaps more important if you want to maintain a healthy gas exchange, both O2 and CO2. But just my opinion it may well be wrong...


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## Manuel Arias (18 Oct 2015)

I agree with Troi.

Essentially, under a low mix of water you are likely to suffer stratification in the water, which basically means that the oxygen in the top will not mix with the underlying water, so any oxygen generated by the floating plants will not help much in the tanks. Best way to compensate this without disturbing _Lemmna minor _is to ensure sub-surface circulation of water by having the outlet from the filter several centimeter below the surface.


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## ajadcock (18 Oct 2015)

Thanks for the replys guys 

So, my spray bar sits about 1.5 inches below the surface firing straight across the tank.

After a spot of faffing bits of debris make it across the tank pretty rapidly in the flow, so I think that part is alright. It just doesn't break the surface!

Troi - What floaters would be better suited to having some agitation?

(PS, my poor photography has made salvinia minima look like lemna minor  go me! )


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## Tim Harrison (18 Oct 2015)

No it was me not paying attention...it looks like salvinia now you mention it I don't think you need worry in that case...


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## ajadcock (18 Oct 2015)

Hehe no worries! 
Cheers! 

Adam



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## dw1305 (19 Oct 2015)

Hi all, 





Troi said:


> I think that you need agitation to get the dissolved O2 in to the rest of the water column, otherwise I reckon a lot will be trapped just under the surface and eventually lost to the atmosphere.


I'd thin the _Salvinia_ a bit. I usually thin it to about 50% cover in the winter when there is less ambient light, and 2/3 coverage in the summer. 

I also run a venturi on the filters.

cheers Darrel


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## ajadcock (22 Oct 2015)

Hi all

I heath robinsoned a venturi on a power head earlier today - instantly removed it  
Took forever to get it to create suction and draw in air and when it did - Bloody temperamental and LOUD! 

Sigh. 

Moving on!

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