Acrylic tank problems

I am not having a good day - got a used large tank last December, finally got all the equipment, put water into it, and was running it last night. While vacuuming debris out of the bottom, I noticed what appear to be CRACKS in the bottom.   It is possible these are just scratches, but I'm feeling like being cautious about putting close to 1600 pounds of water into something that might blow out the bottom. Good thing I decided to put off putting the substrate in until I had everything set up. Tank dimensions are 72"x24"x25"h.

So - how to tell whether I have some scratches, or whether this is a disaster? On the 'be pessimistic, you'll be right more often' principle, assuming that it is a disaster, who makes tanks locally? I notice that Hank has some nice new digs - who made that one?

I'm also having a bit of fun with the standpipe being noisy, but from surfing the web, I think a gizmo known as a Durso standpipe will fix that.

Pics would help, I work in Monroe and could swing by and take a look also.

Hard to tell much - I live just south of Monroe, if you could take a look, that would be fantastic.

That looks more like a scratch than a crack..

You need some scratch not a crack mojo sent your way!

You know for sure its a full crack when you can see light reflecting off the crack in a strip as wide as the glass is thick. Course the only crack I have seen is the one that emptied 30 gallons of water all over my garage in under 2 hours so... sending tis a scratch not a crack luck your way!

Looks like a couple of scratches. Did you happen to do a leak test outside before bringing it in? If you did , and it didn't leak  then these would definitely be scratches. If these where cracks the bottom would have failed with a tank full of water. There is no way a crack on the bottom of a tank would have held with that much weight on top.

No, didn't check it before bringing it inside - note to self, should have thought of that, sounds like a lesson from the school of hard knocks. This is my first large tank, and my first acrylic tank, so newbie mistakes are likely.

I had it full of water and running for about an hour last night, and then it took another hour or so to siphon back out. Maybe a good test would be to put something at where the ends are now, fill it back up, and see if they grow. If not, that's a positive sign. I need to fix up a few leaks in the plumbing and try again in any case.

well since its on the bottom and wont be seen if you add a substrate, try wet sanding it a little bit. try a few different grits so you can slowly buff it out. that way if it cleans up you know its just a scratch and not a crack. just my two cents.

Also a good idea - thanks! Everyone here is awesome - a first large tank with sump has been quite the adventure.

You can do it dleblanc! Any issue, questions or concerns we are here. I also live pretty close to you and willing to help if needed. Im a total sump and DYI nut!

Hey man sorry for not getting back to you :(got called into work early. If you have time before noon tomorrow let me know. One way to tell if it is a crack or a scratch is a crack will reflect silver when looked at from a angle a scratch will not show other than on the surface.
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From the picture, I'm certain I don't have a full crack. However, after some discussions with Cory, I think I'm going to opt for safety and bite the bullet and get a new tank.

My reasoning -
1) I want to be running about 1200 gph, my single overflow of 6" square isn't cutting it, and with a single overflow, any reduction in the return capacity could end up with a lot of water on the floor. I think running an overflow at capacity is likely not a wise plan.

2) The tank is 3/8", Cory thinks 1/2" is correct for that size. From the way the front bows, I think he's right.

3) There is very minor surface crazing, and some more minor crazing along the seam to the top panel - this may not indicate imminent disaster, but it is a sign of age, and I can't very easily swap out a tank later. This has been a HUGE amount of work to set up, and once I get fish in it, I only want to dink with it, not do major surgery.

I think I'll run the old one long enough to get the rest of my equipment set up and in place, waterlog my driftwood (which floats despite fairly large rocks attached to the bottoms), and then swap it out.

Thanks again for all the very prompt help!

dleblanc wrote:From the picture, I'm certain I don't have a full crack. However, after some discussions with Cory, I think I'm going to opt for safety and bite the bullet and get a new tank.

My reasoning -
1) I want to be running about 1200 gph, my single overflow of 6" square isn't cutting it, and with a single overflow, any reduction in the return capacity could end up with a lot of water on the floor. I think running an overflow at capacity is likely not a wise plan.

2) The tank is 3/8", Cory thinks 1/2" is correct for that size. From the way the front bows, I think he's right.

3) There is very minor surface crazing, and some more minor crazing along the seam to the top panel - this may not indicate imminent disaster, but it is a sign of age, and I can't very easily swap out a tank later. This has been a HUGE amount of work to set up, and once I get fish in it, I only want to dink with it, not do major surgery.

I think I'll run the old one long enough to get the rest of my equipment set up and in place, waterlog my driftwood (which floats despite fairly large rocks attached to the bottoms), and then swap it out.

Thanks again for all the very prompt help!

  Sounds like a good plan.



"1) I want to be running about 1200 gph, my single overflow of 6" square isn't cutting it, and with a single overflow, any reduction in the return capacity could end up with a lot of water on the floor. I think running an overflow at capacity is likely not a wise plan. "

Good point. However, there are safe guards to prevent overflow of the tank and sump no matter what happens to the system. 1) Never have more water in your sump than the tank can hold. 2) In case of a power outage your overflows should be set to stop syphon BEFORE the sump is completely full. There is a balance between the two.

There's a third thing, which I still need to do - set up a low water level switch so that the pumps never run dry. Prevents damage to pumps, and limits the possible overflow.

With this particular tank, there's very little room between the top of the tank and the water going into the overflow, especially with a higher flow rate than 12" linear overflow length should handle. So if the sump ended up in the tank with a plugged (or even impeded) overflow, there would be a mess, no way around it.

Also, one thing I did that helped prevent disaster was putting one way valves just past the pumps - my returns could have siphoned into the sump otherwise.

This stuff is tricky...

btw, in my opinion. The first rule is never rely on a 1 way check valve for sumps. 1 snail in the check valve stops it from closing when the power goes out.

Aquarium Co-Op wrote:btw, in my opinion. The first rule is never rely on a 1 way check valve for sumps. 1 snail in the check valve stops it from closing when the power goes out.

+1

Having the water return so it barely rests under the waterline is the only sure way not to floOd a sump due to siphoning through the water return when the power is off.

fishNAbowl wrote:

Aquarium Co-Op wrote:btw, in my opinion. The first rule is never rely on a 1 way check valve for sumps. 1 snail in the check valve stops it from closing when the power goes out.

+1

Having the water return so it barely rests under the waterline is the only sure way not to floOd a sump due to siphoning through the water return when the power is off.

That and siphon breaks! I've seen so many people forget siphon breaks it's not even funny.

I know in general what a siphon break is, but how would you construct one for a return?

Aha! Quick search told me the answer. So, I already have a solution, just need to do things right - I didn't want a super strong jet of water coming out of the returns, so the first thing I did with my Loc-Line returns was tee it out. I pointed one down, the other at the surface. If the water level fell very far, the upper one would suck air, breaking the siphon. I think this is likely a better solution than a small hole, which will get clogged with crud, where a nice big return nozzle will not. I didn't intend my design to solve this problem, but I do love it when a plan comes together :-)

dleblanc wrote:I know in general what a siphon break is, but how would you construct one for a return?

At least in my old drilled tank, I had the return bulkhead near the top of the tank. The actual return was a small pvc elbow with a length of pvc attached to it, then a nozzle on the end of that so that I could rotate the pvc and point the return anyway I wanted. At the top of the elbow I just drilled a small hole, small enough that it didn't affect the flow at all. If somehow the return started to siphon water back, it could only drain about an inch or so before the siphon break started to suck in air.

I've seen the same thing but with an airline check valve glued into the piping, so that the water pressure from the return would keep the airline shut, but if it started to siphon the negative pressure would open the valve back up and break the siphon.

The few times I tested it the whole thing worked great, but luckily I never had to test it out for real. I had 2 ball check valves in place, along with a float switch. Maybe a bit of overkill, but since I live on the 2nd floor of a building built in the 1800's, I didn't want to risk anything.

fishNAbowl wrote:Having the water return so it barely rests under the waterline is the only sure way not to floOd a sump due to siphoning through the water return when the power is off.

dleblanc wrote:Aha! Quick search told me the answer. So, I already have a solution, just need to do things right - I didn't want a super strong jet of water coming out of the returns, so the first thing I did with my Loc-Line returns was tee it out. I pointed one down, the other at the surface. If the water level fell very far, the upper one would suck air, breaking the siphon. I think this is likely a better solution than a small hole, which will get clogged with crud, where a nice big return nozzle will not. I didn't intend my design to solve this problem, but I do love it when a plan comes together :-)

I learned this lesson the hard way in my very 1st tank set up. My 1st tank was free  56 gallon that I had to learn to plumb. I got into the hobby by chance by excepting an offer by my boss for an old saltwater set up.

Good thing I'm getting a new tank - this one cannot be run without risking a spill. I had figured sumps were tricky, but they're quite a puzzle.

I figured that while I am waiting on the new tank, I'll just use this one to make sure that all my plumbing works, no leaks, get electrical stuff all hooked up, and so on. I got my last 2 leaks fixed last night, it was late, so I turned off the pump, and went to bed.

Cory is right - stupid check valve doesn't make a solid seal, and it slowly seeped back into the sump. Thankfully, I had arranged the returns to where they would make a siphon break, or it would have been much worse. With this particular setup, there is no water level which allows the pumps not to run dry _and_ will not overflow in the event of a power failure.

I can think of a couple of workarounds - I can put a 90, or a couple of them, to raise the effective level of the returns. The second thing I can do is to drop the partition between the refugium and the area where the pumps pick up, and I think that will let me run at a slightly lower water level.

The other problem that I had suspected might be an issue has turned out to definitely be an issue - the overflow is only 12 linear inches, and to get the flow rate I want, this raises the level in the tank quite a bit, which in turn puts pressure on the sump to have to handle more excess. So for anyone reading who might be considering a sump setup, be cautious with this, and make your overflow larger than minimum.

When I re-plumb for the new tank, I am considering just removing the check valves - they create a head loss, and don't seem to do any good. Or is there some benefit to not having an immediate reverse flow? Also, I'm using a clear swing sprung check valve - are the ball check valves any better?

I seem to keep getting smarter every day...

Damn good thing it is all on a tile floor, and I have an old style mop and bucket...