Re: Aquatic Plants Digest V1 #285

Earl did use a whole lot of pottery laterite in his 220 gallon tank with 
his undergravel filter, and it did clear up in about 3-4 weeks.  It did 
take a while.  Before that, he also had a 100 gallon tank set up with 
pottery laterite and undergravel filter, which also cleared up in about 
3-4 weeks.  In his 220 gallon tank he has half set up with undergravel 
filter + laterite, and half with undergravel heater + laterite, and he's 
trying to see if there will be a difference in plant growth.

When I had my undergravel heater + pottery laterite running, using about 
2 to 3 times as much laterite as Dupla reccomends, there was not a 
problem with water circulating through the gravel and laterite mixture.  

One thing I suspect the undergravel heater + laterite (or even just 
gravel + laterite) will do for a tank is denitrification.  Just as in a 
Joubert substrate, used in marine reef tanks for denitrification, I 
suspect the slow diffusion or flow of water through the gravel may 
encourage denitrifying bacteria to grow.  I'd like to hear opinions on it 
this possibility. 

--  Phillip Smelt
    psmel at sunny_ncmc.cc.mi.us