if you're wanting to drill the tank and reseal it, drill 1st, reseal second. the logic is simple. if you reseal the tank then try to drill it and the panel shatters, you've wasted time and effort and money resealing it.
the average person can reseal a tank pretty easily if they're willing to put the time into prepping the surfaces.
Items you'll need (provided this IS a glass tank, not acrylic)
a box of single edge razor blades
a Box (or at least bag of 10 pair) Surgical gloves
1 roll of blue masking tape (the blue seems to work the best on glass)
a small can of acetone (this releases harmful fumes and in an unventilated are can kill you)
a pack of scotchbrite pads (the green scrubbies, generic is fine)
1 caulking gun
2 (that's TWO) tubes for Silicone sealant the Sealant CANNOT have Biogard or it will kill your tank's occupants ( DOW 79 (black) or 799 (clear) or even OLDER tubes of GE Silicone I (read carefully to see if it has any type of mildew inhibitor)
Some type of respirator or air filtering mask
Several plastic spoons and a container of water
About 2 weeks actual time and about 6 hours to do the actual resealing (can be split up except for the caulking)
Since you'll be drilling the tank I will "assume" you know how to do that and will go right to the resealing
1, stand the tank on it's end on a FLAT LEVEL surface. Place cardboard down or a towel to prevent any scratching of the glass
2, using the razors, remove all the fillets of existing caulk from the sides and bottom edges of the tank (dont worry about the top rim).
3, Using the acetone, green scrubbies and a pair of gloves, wash and clean all seams on the inside of the tank until they are PERFECTLY clean. clean outwards from each seam by a minimum of 3"
4, allow to air dry for a minimum of 4 hours
5, mask off each seam so that only 3/4" is exposed between the actual seam and the closest edge of the tape. These will be used to give you nice looking seam edges. Make sure you have a small piece folded over to be able to pull the tape off.
6, load the Caulking gun with 1 tube and have the other tube ready to change out. (most Caulk will have the end sealed but also some of the silicone will have hardened that will plug up the tip. hole size should be about 3/16-1/4"
7, with a new pair of gloves and the respirator or mask on, start running your bead on the bottom edges of the tank and then do each of the side seams. a bead that is 5/16" or slightly smaller is all you need. Do NOT go past the blue tape or that will be something else you have to scrape off later.
8, Once all seams are finished, grab one of the spoons, dip it in water and using the bottom radius, start forming the fillets. if the silicone seems to drag or hang up, dip the spoon in water again. Again, start on the bottom edges of the tank then progress up the sides. if one spoon starts to have silicone buildup, throw it out and grab another spoon
9, When all the seems are smoothed out and filleted, allow then to tack up for about 5 mins. then start removing the tape. work quick here pulling the tape towards the center of the tank and have a garbage can handy
10, allow the silicone to cure for 10 DAYS. This will give you the strongest possible cure and will also allow the acetic acid (it smells like really strong vinegar) to leech out and evaporate. ( I skimped on this part on my 120, please read my signature)
11, set up a temporary stand that is SOLID. fill only 25% of the tank with water. look for leaks. allow that to stand like that for a day. repeat this for 50%, 75% and finally 100% (plug the holes you drilled earlier)
for the 100% fill, allow this to stand for a MINIMUM of 2 days and scrutinize it for ANY LEAKS. If this passes, drain the water, wipe down the tank and clean then set it on your permanent stand and plumb.
