sump baffles, how small is too small?

[Dave A]

I'll be building a new sump from a 20H and I found that I already have a piece of 3/8" tempered glass that's just a little bit smaller than one of the baffles that I need. How much can I fudge it by using a thicker bead of silicone? I haven't measured yet but I'm probably short by a quarter inch on each side.

 

[Glenn]

That will mostly depend on the height difference between the higher side and the lower side of the baffle. If one side is 10" and the other is 2", that would be a lot of pressure and the silicon may not hold. If the low side is 7-8" then there won't be as much pressure and it MAY hold.

 

[Dave A]

Thanks, it's square, probably about 11-11.5" so one side would be that high and the other would be about half that. Sounds like I'd be pushing my luck with it. I haven't assembled anything like this in at least 20 years so I'm a bit rusty. IIRC, about 1/8" all around is what I want?

 

[Planedoc]

I built a sump with 1/4 inch gap on each side of baffles. I never had a problem but I was careful when filling it to keep water levels close to even on each side of baffles

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[Dave A]

I just got a chance to check, the piece in question is 11.25 square, the inside of the tank is a hair over 11.75 so an extra quarter inch on each side. I'd hoped to use it between a center return and a small fuge section on one end. Due to limited space there will probably not be a divider between the skimmer and return, certainly not a bubble trap. Unfortunately the sump has to fit into a 26" space so I'm limited to a 20H.

 

[Planedoc]

Thick silicone takes a long time to cure. When I did mine I ran a 3/16 bead on each edge of the baffle and let it cure for a couple days. Than I installed it in the tank. It worked out great. It's important to have a baffle after skimmer so the water level stays constant in the skimmer section. If not your skimmer will never work to its full potential

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[Dave A]

I agree that the baffle is important and I'll add it if I can find a way. Unfortunately, I'm forced to cram what should be a 36" sump, into a 12x24 tank. My ATO is set up to keep the water level within 1/4" but a baffle would be a nice fail safe. The down side is that it would leave me with only 15" for the return and fuge sections and a small return will fluctuate very rapidly.