I took a risk. 425 craigslist rebuild

  • We are currently upgrading MFK. thanks! -neo
fishguy306 said:
Some things to keep in mind, what kind of silicone are you using? If it is GE I or II it is junk, I would not trust that much water with that stuff, I would get some quality silicone such as RTV 103 or 108. Also, silicone does not stick to acrylic which is why you would have leaks.
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Just curious, what's the difference? Aren't they both 100% silicone?

Also I built a small (5g) tank shaped like an "N" out of nothing but acrylic and silicone and it's held together solid with no leaks for over a year. I know it's not the same as 425, but that one didn't have any bracing whatsoever. Literally acrylic and GE silicone.

I was pleased to find out last night while cleaning up the inside of this one, that the lexan is held in place with bolts instead of JUST silicone or adhesive of some kind. So it's good that at least the silicone I'm adding won't have to hold it in place, just stop water.
 
The bolts make sense, it uses the silicone as a gasket rather than an adhesive. You can probably get away with the GE stuff in this case, though I would still go the RTV route.

GE I/II and RTV 108 are not the same. GE silicones are sealants where as RTV 108/103 are adhesives. One is designed to block moisture, the other is designed to hold objects together. I don't have the numbers in front of my to give you but there really is no comparison between the strength of GE I/II and the RTV series.

As for holding your acrylic tank together, my guess is there just isn't enough pressure to push it apart. It will have some holding power, but not the levels of a glass tank built the same way. It is a dangerous game to trust silicone to hold acrylic together.
 
Understood. I will say for the $10 it cost me, I'll test the GE and see if we get leaks. With three coats, I would assume not, but you never know, and like you said, it's just made to stop water, not adhere things. I mean the original leaks were pinholes along the bottom edge, looking in it I could see where the silicone simply got peeled off, probably from sitting outside in the Phoenix sun for a year. But while a pinhole isn't bad now, it can obviously get worse.

My plan is to leave it in the garage for a month to leak test it. If it holds up, great. If not, I'll redo it with RTV.



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fishguy306 said:
Sounds like a solid plan. Are you going to or did you remove all of the old silicone and reapply? Just another thing to keep in mind, new silicone does not adhere to the old stuff.
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Oh yeah! I learned that real quick in my first 5g build. It was a *****, but I removed all the old silicone with a knife then wiped it down to remove all the extra flakes then let it dry then applied the 3 coats 4-6 hours apart

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So......slight hiccup. I've been using GE silicone 2 with mold inhibitor without realising. I literally had one more coat to put on the inside before leak testing. Oh well. Time to strip it all out and redo it the inside seals with the right stuff. I might just splurge the extra and get rtv 108 if I can find it. Was planning to have this up and running by thanksgiving but that might not happen...

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The mold inhibitor killing all your fish is a myth. As long as you let it fully cure it is fine, however the RTV is a far superior product and what I would use!
 
muttley000 said:
The mold inhibitor killing all your fish is a myth. As long as you let it fully cure it is fine, however the RTV is a far superior product and what I would use!
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False....i used ge #2 back in 07-08 when it came out and witnessed the effects first hand. The fish's slime coats and skin began to melt off after a couple weeks in the tank. Ugly, bloody looking mess with fish twitching around convulsing. Once removed the fish recovered quickly. Luckily i saved most of them in time. It was 100% the ge#2. There is ge #2 sold without mold inhibitor out there so its more likely u used one of those muttly instead of a mold inhibitor. O.P. take the time to strip it down/out for a redo or it may be possible to cover it up with fish safe silicone. I do agree the RTV is far superior to Ge1 in general but the mold inhibitor in ur fish tank is common sense not too.
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That's the plan. I couldn't get ALL the old silicone off, but I got enough that I'm going to be able to cover it completely with RTV. I'd have already had a coat or two on by now but the only place that sells it around here is Grainger and they're closed Sunday. :(

Good news is this has given me time to think of how to filter this baby. Conclusion: I still have no idea apart from hooking up the FX6 currently with the catfish....

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