Aquarium back panel separation

New2Reefing22 · Apr 9, 2026

So this was a used tank we purchased a few years ago. I never noticed that one side of the back panel seems to be sliding off the bowfront. Is this something to be concerned about. It is possible that I never noticed it before because I don’t check back there often.

MikeReefs · Apr 9, 2026

That second pic looks sketchy

UncommonSense · Apr 10, 2026

Could we get a well-lit photo detailing the top-exterior of that rear right silicone seam?

It’s tough to say from your photos, but I think I see a physical crack in the silicone…

New2Reefing22 · Apr 10, 2026

I’ll try to get better picture tomorrow. I think I’d rather be safe than sorry. Should I just take down the tank?

TangerineSpeedo · Apr 10, 2026

Yes... time for a new tank... although it is weird that the top half is moving, when most of the pressure is lower.
You could alway repair it, but if your not handy than it would not be worth it... May not even be worth it if you were.

UncommonSense · Apr 10, 2026

I’m only wondering if it’s actually an assembly defect, I’ve definitely seen some sloppy pane alignment before!

Though, more likely is silicone failure… I agree that the location is odd… possibly due to it (at least appearing to be) a rimless bowfront with monolithic front/sides… that’s the easiest place for such a tank to start spreading apart!

New2Reefing22 · Apr 10, 2026

It’s weird cause there is some bracing at the top and it doesn’t look like the silicone is cracking but it’s definitely significantly misaligned.

UncommonSense · Apr 10, 2026

New2Reefing22 said:
It’s weird cause there is some bracing at the top and it doesn’t look like the silicone is cracking but it’s definitely significantly misaligned.

More photos might help work out what’s actually happening here!

New2Reefing22 · Apr 10, 2026

Here are some more photos

Uncle99 · Apr 10, 2026

What’s the total volume in that tank?
What’s the device in the corner?
Could it have already been repaired there?

Personally, I’d be safe and take her down, it look like the panel is being pushed.

Reefing102 · Apr 10, 2026

I personally don’t like it.

But if it’s a true bowfront, I can’t say I’ve ever seen a bowfront that’s nots fully rimmed (extrerior trim bracing not what appears to be euro braced). I’m curious if the prior owner removed the original trim and DIY’d the interior bracing.

UncommonSense · Apr 10, 2026

New2Reefing22 said:
Here are some more photos

It’s still hard to say exactly what’s going on here…

I think I see a eurobrace, but can’t tell… if that is a eurobrace, it should be reinforcing that entire corner!

Operative word here is “should”… if the silicone holding the euro bar to the short side wall of the tank has ripped free, the entire corner could start ripping apart, as you’re seeing…

— I’m leaning towards proactively taking this tank out of service… I’m curious if that rear pane comes back into alignment as the water is drained…

New2Reefing22 · Apr 10, 2026

It was sold as a 69 gallon. It’s really a bummer because the tank was just starting to come together well.

UncommonSense · Apr 10, 2026

New2Reefing22 said:
It was sold as a 69 gallon. It’s really a bummer because the tank was just starting to come together well.

First off, this tank is awesome!!

Secondly, wow! That back panel looks like it’s made of plastic! Not good. It’s bending.

Third, This:

Do you see that light grey area near the exterior of the silicone seam? That’s tearing!!

This tank is getting ready to fail… I strongly recommend sourcing a stock tank or other reliable water holding tank/container as soon as possible to proceed with rock/livestock transfer, before draining this tank and decommissioning it!