I have some weird reddish/brownish things stuck to the silicon in my 6.5 gallon tank. They can't be removed and seem unbreakable. I just noticed it today because the seam that they are stuck to are behind a large peice of driftwood and coved by plants. They almost feel like large grains of sand embedded into the silicon.
The tank is co2 injected and the ph is sitting at 5.5
temp is 76
no ammonia or nitrite readings and nitrate fluctuate between 10-20ppm