Purple in my substrate

Southern Rebel

Gambusia
MFK Member
Apr 24, 2012
352
0
16
TN,USA
This appeared tonight sometime after I fed my Africans some flakes in the 55 gallon...the substrate is eco complete African cichlid sand and there's a small spot that is bright purple but you can't tell its that bright in the picture but it is lol what could this be?

 

Southern Rebel

Gambusia
MFK Member
Apr 24, 2012
352
0
16
TN,USA
well it was gone this morning..I do keep my lights on for 16-18 hours everyday but only in hopes to grow green algae on my rock for my africans to eat.
 
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