Second hand tank repair

[Blu3Shyft]

I got this used tank+stand for a steal at a local fish store. Since it was such a deal for me, I'm not loosing any sleep over the condition, but when cleaning it up today (had to replace the top cross support/frame too) I notice some pretty deep scratches around the inside of the tank. I'm thinking the previous owner had some rougher rocks as decorations. I think it was a salt tank.

These scratches are deep enough I can catch my fingernail on them, so I don't think the normal polish or toothpaste methods will work. What other options are there with a Near Zero $ budget?

Also, when cleaning it I found that some spots of the caulking in the corners are coming up and fraying, and some spots are getting discolored. So far as I can tell, the tank is still water tight, but I don't want to take a risk of 46 gallons leaking out on the floor.

I picked up some marineland Aquarium Sealant silicone rubber stuff to seal down the top frame, and I'm wondering if I should peel up the loose stuff and apply this new stuff, or just leave it as is? What would you do?

(side note, the spots on the glass are from this 'aquarium safe cleaner' I picked up from Petsmart. I think I'll take it back and go the vinegar route)

 

[Karay]

I can't say anything about to repair scratches but as to the caulking new silicone does not adhere to old silicone. Best solution is remove all the caulking on the interior glass and reseal it. But be careful not to remove any caulking that holds the panes of glass together.

 

[Fishfur]

You might be able to put epoxy putty into the scratches.. but it's not the cheapest stuff around. Oatey's brand is much cheaper than the stuff sold for aquariums. It's quite safe, but it's an ugly tan colour. If it will be under substrate that won't matter. Cures very fast so you have to work quickly, only two or three minutes working time.

Test fill the tank to check for leaks. If you get any, you have to reseal. It's quite a job, and you'll need a lot of razor blades for a scraping tool, as well as some plastic scrubbie things. It can take a long time to scrape all the silicone off.. and you have to get every last scrap or the new stuff won't stick. I use a vacuum cleaner to suck up the bits.. way easier than trying to pick or wipe them up.

Don't let the blade go below the glass level, into the join between the panes, that is what actually holds the tank together.

Tape is very helpful to get nice even lines when you apply the new sealant, and you'll need a caulking gun unless it's in a squeeze tube.

You need to run a bead along the cleaned joining edges, then smooth that and press down with a finger, squeezing the caulk down to nothing at the taped line, and it need not be more than 1/8th inch thick at the joined edges.

Any excess goes onto the tape. Remove tape the instant you finish. If you let the sealant skin over while the tape is still on, it will take the new sealant off when you do remove it. So remove it right away. If you get any smears, let them cure, it's much easier to get them off once dry than to do it wet.

The scrubbies can help to get the last little bits of old silicone off, once you've scraped off all you can. It can take several passes over a given area, and once the blades get dull, they won't work for the really thin stuff, though they'll still be ok for removing large chunks of old stuff. No solvent will remove it, so using acetone or alcohol only cleans the glass, it won't remove the silicone.

I bought a box of 100 blades, having several tanks to do, and I'm about half way through them after three tanks, none larger than a 29G. I found a long handle bent scraper worked better for me than a short straight one, and a very short handle one was best in corners.

Patience is the key.. it can seem like it's taking forever, but you'll get all the old stuff off eventually. Then clean the glass really well, to remove skin oils, grease, anything else that might interfere with new silicone. Place your tape lines and trim the corners so they are neat and square. Overlap them so when you remove the tape, the first row will lift the second row at the corner and so on. Before you start with the new sealant, also remove the rim. Clean out any hot glue or old silicone. There usually isn't much. When you are done with the tank sealing, fill the rim channel with silicone, and stick it back on. It will prevent any water from ever wicking up and out if you fill the tank to the top. If any squeezes out, just smooth it under the rim edge.

 

[Karay]

That's a really comprehensive explanation. I like the info on how to press the silicone into the joint where the excess goes on to the tape. Thanks

 

[Fishfur]

I'd try practice on a box first. It is not a hard skill to pick up, just a bit of tryout will tell you how hard to press, and how big a bead gives you what you need without too much wasted in squeeze out.

Just run about a quarter inch thick bead in the join, then run a finger along on top of it, pressing down but not too hard.. you will get a feel for it quickly enough.

You don't need a thick layer of the stuff, it's mainly insurance for leakage, as it does not hold the tank together at all. That's done by the silicone between the panes themselves. The extra layer inside is really just insurance.. and a number of really high end tanks don't have any silicone on the inside at all. Just between the panes.

The thinner the layer, the neater it will look once done.. you want it to slope down to the inside edge neatly, so the inside edge is feathered down and firmly stuck to the glass. If you make it too thin, then the edge may lift later. Not a big deal, but dirt and algae can get stuck under a lifted edge, and look untidy. Hard to clean out too.

You'll figure it out pretty quick once you try it a few times and you'll probably only need a few inches of practice to get it.