I purchased a java fern about a month ago. I noticed that it started to grow these strange brown strands. I was wondering, is this normal? Is this something I should worry about?

I don't see anything in the photo, but if it's growing brown strands under the leaves, that is how the plant propagates. the brown strands are the roots of baby plants. Soon you will see little tiny baby leaves and it will eventually detach from the mother plant and float around your tank until it finds somewhere to root.

Nothing to worry about.

Edit: On closer inspection, that is exactly what is happening. You could actually detach those yourself just by running your finger along the mother leaf.

I've heard them called crampons... Ya learn something new every day!... Bill in Va.

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12 Tanks, 900 gallons. Discus/Angels/Malawi/Lake Victorias. Just added a 135 & 2 - 29's..