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Old 11/09/2017, 12:55 PM   #26
Shamous113
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I would advise against using acrylic in a glass sump. The quote below is from RocketEngineer on reef central found in this thread,

"ACRYLITE FF sheet also absorbs water when exposed to high relative humidities resulting in an expansion of the sheet. At relative humidities of 100%, 80% and 60%, the dimensional changes are 0.3%, 0.2% and 0.1 % respectively."

So, think about that for a moment. The vendor of the material claims a 0.3% expansion of the sheet at 100% relative humidity (a.k.a. immersion). That means for a baffle 10" long, that sheet will expand 0.030" Or ~1/32".

Now, lets figure out what kind of force that would cause:

Y=(F*L)/(A*DeltaL) where:
Y=Young's Modulus (400,000psi for acrylic)
F=Force (lbs)
L= Length (baffle length = 10")
A = Area (Assume 10"X 0.25")
DeltaL = Change in length (0.030")

Rework the equation:

F = (Y*A*DeltaL)/L = 3000#s

That's right. 1.5 TONS of force are pushing on the inside surface of that pane of glass due to expansion of the acrylic.......... And its right in the middle of the glass along a very narrow region.

The moral of the story is don't mix materials when the ends are constrained."


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Old 11/09/2017, 01:02 PM   #27
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Originally Posted by Bulldog39 View Post
True can I just use a strip of egg crate on top of the last baffle when done to keep the chaeto from going in the return area?

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Old 11/09/2017, 01:03 PM   #28
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An over-under pair of baffles will stop cheato and most fish from reaching the pump chamber. First one is overflow at water level, second one about 3/4 inch away (on the pump side) has a half-inch gap under it.


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Old 11/09/2017, 01:04 PM   #29
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I would advise against using acrylic in a glass sump.
I FULLY agree..


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Old 11/09/2017, 01:08 PM   #30
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I'm sorry, but I just had to laugh when I saw the baffle sizes in relation to the tank height! I mean really, who at that LFS looked at that and said, yep that's good?


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Old 11/09/2017, 01:15 PM   #31
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if 1/32 is the total expansion, don't we normally leave like 1/16 to 1/8" gap on each side for a total of 4/32" to 8/32" room for expansion? I don't think anyone actually cuts the baffle to fit tightly against the walls of the sump. Anyway, OP is going to use existing glass.


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Old 11/09/2017, 01:15 PM   #32
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I mean really, who at that LFS looked at that and said, yep that's good?
An absolute moron.. If I didn't know it was just Halloween I would have thought this was April Fools day..


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Old 11/09/2017, 01:21 PM   #33
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You're asking how to fix it without starting over. And have made 2 threads asking for help. Starting over is the only real option if you want your sump to operate properly.
I think what mcgyver suggested will work, but it involves cutting out some baffles. If you are going to cut out baffles, you might as well cut them all out and do it right IMHO. Either way will involve some work.
Maybe get a new empty tank and start from scratch? Sell this one to someone willing to take the time to cut them out.
For what it's worth, siliconing in baffles is a relatively easy process. Good luck!

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Old 11/09/2017, 01:39 PM   #34
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You're asking how to fix it without starting over. And have made 2 threads asking for help. Starting over is the only real option if you want your sump to operate properly.
I think what mcgyver suggested will work, but it involves cutting out some baffles. If you are going to cut out baffles, you might as well cut them all out and do it right IMHO. Either way will involve some work.
Maybe get a new empty tank and start from scratch? Sell this one to someone willing to take the time to cut them out.
For what it's worth, siliconing in baffles is a relatively easy process. Good luck!

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If siliconing is an easy process, why do you recommend he go so far as to get a whole new tank?? That is way overkill. Sure he'd have to work within the parameters of the glass height he has but it should work just fine.


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Old 11/09/2017, 01:40 PM   #35
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Originally Posted by Sk8r View Post
An over-under pair of baffles will stop cheato and most fish from reaching the pump chamber. First one is overflow at water level, second one about 3/4 inch away (on the pump side) has a half-inch gap under it.
True, but if I understand mcqyvr correctly there will not be a "pair" only a divider. Easier to just have one panel of glass. Also ime you need and inch or so in between baffles to get into them for both putting in the silicone and cleaning.


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Old 11/09/2017, 02:12 PM   #36
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Quote:
Originally Posted by d0ughb0y View Post
if 1/32 is the total expansion, don't we normally leave like 1/16 to 1/8" gap on each side for a total of 4/32" to 8/32" room for expansion? I don't think anyone actually cuts the baffle to fit tightly against the walls of the sump.
That gap then gets filled with silicone, once cured the silicone will only compress so much at which point the the force is applied the sides of the aquarium. IMHO its not a matter of if it will fail but when will it fail.


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Old 11/09/2017, 02:48 PM   #37
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That gap then gets filled with silicone, once cured the silicone will only compress so much at which point the the force is applied the sides of the aquarium. IMHO its not a matter of if it will fail but when will it fail.
It is done all of the time and I have never heard of the sides blowing out. Usually the gap that is filled with silicone is 1/16-1/8 on each side. You also have the bowing effect in the center of the piece. Personally, I like glass so I have never used acrylic. Also I think poly-carbonate absorbs less than acrylic, I know it is stronger.


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Old 11/09/2017, 03:08 PM   #38
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It is done all of the time and I have never heard of the sides blowing out. Usually the gap that is filled with silicone is 1/16-1/8 on each side. You also have the bowing effect in the center of the piece. Personally, I like glass so I have never used acrylic. Also I think poly-carbonate absorbs less than acrylic, I know it is stronger.
Oh.. it happens.. I've seen enough people post pictures on here saying "how did this happen?"..
And you will find that in every case they had the baffles cut way too tight and did not have enough silicone between the acrylic and the tanks glass..

The point that Shamous113 is making is totally valid and I will always recommend glass for glass and acrylic for acrylic for multiple reasons.. Its best to use glass with glass and there can be considerable force placed on the glass due to expansion..
But yes.. by ensuring you don't make the baffle too tight so that expansion forces are not in excess of what the glass can take then you can have a long lasting sump that won't crack when using acrylic in a glass sump..
I'm using acrylic baffles in my current sump.. But that because I know what I'm doing and how to do it safely (I still just knocked on wood though)

And I do think that bulldogs problem would be best solved by removing all the crap they did and getting new glass cut but what I stated before "may" be the best/easiest for them to move forward with something "usable"..


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Old 11/09/2017, 03:11 PM   #39
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It is done all of the time and I have never heard of the sides blowing out. Usually the gap that is filled with silicone is 1/16-1/8 on each side. You also have the bowing effect in the center of the piece. Personally, I like glass so I have never used acrylic. Also I think poly-carbonate absorbs less than acrylic, I know it is stronger.
if you search, you will find a thread where the sump cracked.
I think the acrylic fitting too tight is the real cause, as there are people who say theirs have been working for years just fine.


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Old 11/09/2017, 03:13 PM   #40
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Possible, but have not personally seen or heard of it.


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Old 11/09/2017, 03:20 PM   #41
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Possible, but have not personally seen or heard of it.
It certainly happens.. I'd say I've probably seen 20+ posts here about it in my time on this board..


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Old 11/09/2017, 03:57 PM   #42
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I believe you, I guess I have never cared enough to research it because I only use glass. Even with glass dividers there is a tendency for people to get the thin picture frame glass cut at Lowes. Doesn't take much of a hit to break that stuff.


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Old 11/09/2017, 03:58 PM   #43
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If siliconing is an easy process, why do you recommend he go so far as to get a whole new tank?? That is way overkill. Sure he'd have to work within the parameters of the glass height he has but it should work just fine.
I only suggested a fresh tank because I've cut baffles out before. As easy as it is, it isn't fun lol.

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Old 11/09/2017, 04:01 PM   #44
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maybe you were removing it by scraping the silicone with a blade or knife.
I've seen youtube videos doing it that way. and yes, that is not easy/fun.
if you use a fishing line (or some use guitar string), its like cutting butter with a hot knife. baffle will be out in a few minutes.


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Old 11/09/2017, 04:07 PM   #45
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It is not easy to get the fishing line in between the baffles so that you can use a saw motion to cut them out. Use a razor blade. What really works nice is the blade from a disposable razor. Very thin. I have cut panels from my tank building days out so I know the process too well Regardless how you do it is not difficult.


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Old 11/09/2017, 04:25 PM   #46
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if there are two baffles, one will be over and one will be under.

removing under baffle is easy, just run the line under and slice away.
removing the over baffle you run the line between the two baffles to go under and out the other baffle, then just position the line and slice away.

yes, it will be hard (actually impossible) to get your hand between the over and under baffle.


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Old 11/09/2017, 04:31 PM   #47
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Let's not over think this. Do whatever works to remove a 6" thin glass baffle.


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Old 11/09/2017, 04:35 PM   #48
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the picture in post #1, the return section has 3 baffles. over/under/over

make sure to remove the over first (either one), then under, then over if needed. if you remove the center (under) first, then it will be hard to remove the two over baffles using the fishing line method. don't be tempted to remove the center baffle first.


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Old 11/09/2017, 05:26 PM   #49
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Thank you all I have gotten wonderful advice. Think I will wait yo fix it till the cycle ends and I do a water change so it will empty the sump. Two birds one stone. Thought this was a huge problem but now I have a great idea from the support here. So glad people are willing to help since lfs isn't an option anymore.

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Old 11/09/2017, 06:14 PM   #50
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While the tank is cycling is the perfect time to go ahead & get it done. That way u donít end up rushing & not letting the silicone fully cure before u put the sump back online. Most sumps end up using close to a 1/4Ē bead of silicone & I would let it cure for atleast 7 Days & preferably 10 days before adding it back to the system.


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