I've had my 12 gallon aquarium up for 25 years.  Sometimes as a terrarium, but mostly as a fish tank.  It serves to help put moisture in the air, water my plants, and occasional cats, but mostly as a way to store my antique glass battery case that was my grandfathers.  I currently have way too many fish, Mollies.  They just keep breeding.  I also have 2 shrimp (they've been in for 4 years)  My main problem is lime buildup on the glass.  What if anything can I do to prevent this?  I don't use a light, and have fake plants.   I just removed all the plants for cleaning, that's why it looks so bare.