# Water Flow - A tale of 2 Crypts



## Coastline (May 10, 2005)

I recently bought 2 pots of _Cryptocoryne _ _Undulata_ & planted them at either end of my 36" tank. As expected melt down started after 8 days but the Crypt next to the outflow of the Fluval 104 Filter is virtually intact whilst the other Crypt in more relatively still water flow has had 95% meltdown!!

Any comments would be appreciated.

Thanks

Alan


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## HeyPK (Jan 23, 2004)

Moving water allows for better nutrient and CO2 uptake because in still water, a boundary layer of depleted water builds up next to the plant, and nutrients and CO2 have to diffuse through the boundary layer. In effect, the depleted boundary layer increases the thickness of the barrier that nutrients have to diffuse through, thus reducing the rate of uptake of the nutrients. Given the same concentration of nutrients in the water, plants will get more nutrients if the water is moving. If the water is not moving, you can increase uptake by increasing the concentration of the nutrients. 

All this theory suggests that the crypts near the filter got more nutrients and CO2, and that was why they didn't melt down so badly. It also suggests that increasing nutrient and CO2 concentrations might have helped the plants that were not near the filter.


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## Coastline (May 10, 2005)

Thanks for the comment, it sounds logical as the only difference between the two plant clumps is the water flow.

Alan


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