Substrates: Sand

     A few comments on the use of sand as a substrate for plants.
     I bought a 100 pound bag of sand from the local hardware store for $4. 
     I believe it is usually used for making concrete.  It is light greyish 
     brown and flecked, not blinding white like beach sand, and looks nice 
     and natural. It passed the acid test; I put some in a jar with water 
     and it did not change the pH.  It was rather a chore to clean, and 
     took quite a few rinses.  Now I have my tank set up with 
     sand/laterite/Tetra Hilena-D and am still seeing beautiful growth six 
     months after set up. (Several types of large and small swords, Rotala 
     indica, Hygrophila polysperma). An advantage is that the root systems 
     grow rapidly to enormous size.  This is also a disadvantage, because 
     the bigger sword plants are impossible to move without disrupting the 
     entire tank.  I just pulled up a huge Echinodorus cordifolius and made 
     quite a mess --it had roots 18 inches long.   In the future I will 
     have to decide from the start where large plants will be permanently 
     located.  Even small plants like E. intermedius or quadricostatus root 
     deeply and are hard to pull up without making a mess.
     A possible disadvantage might be the lack of water circulation through 
     the fine particles.  We will have to see what the long term stability 
     is.  My feeling is that substrate heating coils would probably not 
     work well with fine sand.
     When I originally set up this tank I put some sterilized peat and a 
     small amount of sterilized composted manure in.  This turned out to be 
     a bad idea.  In retrospect what apparently happened was that the 
     substrate went anaerobic and produced small amounts of H2S, which then 
     fed a bloom of single cell blue-green algae. (thanx to Shiao Wang for 
     help with this diagnosis). I battled this chronic cludy water 
     situation for several months, then gave up and tore down the tank.   
     If the tank is densely planted right from the start this may not be a 
     problem, but I would not be inclined to put a nitrogen source down 
     there again!
     Someone (Erik, I think) mentioned that sand substrates are bad for 
     Corydoras, but I have not seen this.  I have a shoal of Corys which 
     love to root about in the sand, and their whiskers are intact.  Other 
     types of sand may have this problem, but not this stuff.  
     Sand does not need vacuuming the way gravel does, since detritus just 
     sits on top.  Again this is also a disadvantage, as it does not hide 
     the junk, and can make things look a bit unkempt.
     Right now I'm battling a form of algae which grows out of the sand in 
     green filaments with length a cm. or less.  This stuff goes fairly 
     deep into the sand as well, and is very difficult to  extirpate.  I 
     don't have any Epalz. siamensis (SAE's), but neither Pleco (actually 
     Pterigoplicthys) nor Otocinclus care for it.  It is very unsightly.  
     If anyone has comments on this nasty stuff I'd be most interested.
     Up to the minute news:  almost two weeks ago I put in some Crypt. 
     wendtii and pontederifolia, under a huge melon sword.  Both types 
     started producing healthy new leaves within days.  The pontederifolia 
     is now producing runners and sending up new plants amazingly quickly. 
     By contrast, I tore out a mat of Echinodorus intermedius and 
     replanted the best looking ones, a la George Booth.  These are not 
     growing with anything near the alacrity I expected, and after two 
     weeks have yet to produce any runners.  What might be happening here?
     That's enough rambling for now.  
     A big round of kudos to Shaji and the others who started this list!
     Regards to all
     Bob Hoesch
     National Fish & Wildlife Forensics Laboratory
     Ahsland, OR
     HoeschB at fws_gov