Silicone Seal on our 75 Gal

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MarkoSolo

Feeder Fish
MFK Member
Jan 25, 2020
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We were given an old Schooner 75 gal tank - super cool but.. the previous owner said it had been in a crawlspace 15yrs but held water when he used it last. The silicone along the vertical edges has some black 'funk' that will not wipe off with a sponge. Thought it might be mold, but not sure if we should use it. 75gals of water could be a bit of a problem if it leaked on our second floor townhome..! I am slowly filling it to see if it leaks, but concerned that whatever the black stuff is could affect the fishes environment - suggestions?

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I would never trust a tank of this age and silicone in that condition.
I would suggest that you cut the tank apart and re-silicone it.
It’s not as difficult as it may appear.
I can explain the process if you’d like.
There are lots of videos on how to accomplish this.
if that would be more informative.

I’ve made many tanks and resealed dozens.
Most people use the silicone GE1 for windows and doors.
Do not use GEll (or GE2) it is known to contain mold inhibitors that can be deadly to aquatic life.
 
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So after a few videos, it seems pretty easy and I would be totally comfortable doing that- my question would be then, is removing the silicone and replacing it enough? Do I need to be concerned with rebuilding the tank (taking it all apart and putting it back together) - at that point it may be easier to simply purchase a new one for $150.
 
I would rebuild that tank not just reseal. The silicone between the glass is what actually holds the tank together the inside seam is more or less to just reinforce the seal.

Weather it’s cost effective to you is something you will need to decide for yourself.

I think it’s worth the effort because with a little work and 10 buck worth of silicone you can have practically a brand new tank.
 
With a job like this prep is key to a good repair .
You will need to be sure that all silicone residue is removed.
It just takes some razor blades and a little time.
I also clean everything with rubbing alcohol before I re-seal.
 
All makes sense - the tank has some white plastic strips at the bottom (you can see them in the first photo) I am guessing these were there to help place the side pieces accurately - the glass is 3/8" so pretty heavy - would it be worth removing those? seems like since they are not part of the seal that would not be necessary - leave them and simply reattach the sides. There are also pieces of black plastic top and bottom - more for aesthetics I think, they are not a solid frame (the cover is plexiglass and siliconed to the tank so that provides structure). Does it sound like I am on the right track? (and thanks for your time responding to this!!)

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The black stuff could be mold or leftover algae from the previous owner, a regular plain bleach/water mixture may remove it or you can try regular household hydrogen peroxide.

Before deciding whether to fix the tank, make sure the glass is clear and not etched by water deposits or age. Just clean the glass both sides, fill with water and inspect the glass to determine if you can live with any imperfections when you view the tank. A good light held above the tank filled with water will give you the answer.

I have never seen a plastic top frame like that, it looks almost DIY except it has the framing for glass lids. Also not sure what the white plastic trim is on the bottom of the tank.
 
Lol. I know their are some really handy DIY guys on here. When looking at a 75 I would Just wait until they are on sale at Petco and snag a brand new one. Having never broken down and resealed a tank I wouldn’t trust my abilities.
 
Looks like this tank was diy.
Probably someone else has added the trim and acrylic tops.
I doubt that the trim is doing anything for the structural support of the tank.
I would just start cutting the old silicone out and see if if you can slip a blade under the trim and remove it.
Break the tank down into individual pieces.

I enjoy making things and saving old tanks.
So stuff like this is just part of the hobby to me.
If the time involved begins to out weigh the cost of a new tank, you can always stop.
 
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