Building a DIY HOB! Are all acrylic aquarium safe?

[redknight]

I have a Fluval Edge 6g and I'm trying to build a custom HOB filter. The filter that came with the tank is fine the only reason I want to build a DIY HOB filter is I want it deeper so I can put the heater into it. I was wondering are all acrylic safe to use. Plan on having corals, live rock, and live sand so just want to know if its safe. I was going to pick some up at Home Depot or something and didn't know if the stuff they carry was safe to use. Also what kind of adhesive/caulking should I use? Thanks in advance for all the help!

[evilc66]

Acrylic is perfectly safe. It only comes in two main varieties though; extruded and cast. Extruded acrylic is what you find at hardware stores, and is cheaper than cast acrylic. Cast is prefered, as it's stronger and more stable in water. To get cast acrylic, you would have to go to one of the many online vendors (Tap Plastics, US Plastics, etc...) or find a local plastics shop. Going that route is probably prefered due to the fact that they will have the solvent adhesive, while hardware stores will not. Shipping will be a bit of a pig if you have to order online though.

 

Solvent adhesives like Weld-On are the only option for bonding acrylic. Caulk, silicone or otherwise does not stick well to acrylic, so don't even think about using that unless you like wet floors and empty tanks.

[Beer]

There are silicone type adhesives for acrylic, but they are not suitable for aquariums and they really don't hold well. I've tried it several times for various projects and the joints can't take much pressure (I've built several aquariums, so I'm familiar with how to use silicone and followed the directions for the acrylic adhesive. I think that stuff is intended more for using lean to replace broken window panes)

 

Like Evil sad, you want to go with a solvent to bond the acrylic. The cheap stuff at HD (the more expensive, strongest stuff they have) is extruded will work and will be okay, it won't look as good as cast and may haze somewhat. It does tend to be a little weaker, partially due to the strength of the material and partially due to the difference in actual thickness. Extruded has slight variations and the stuff carried in the big box stores tends to come from China, so you get rounded up metric measurements and lower quality control standards. So if you don't care about looks, you should be fine using that stuff since the size of what you are building is fairly small. You are going to have to go elsewhere for the solvent though.

 

If you don't have the tools to get precise, clean cuts, going to a local dealer or an online vendor will be the way to go. Make sure you let them know that you are building a watertight box and need the measurements to be precise. The score and snap method will require way too much prep work to solvent weld the joints and you need the edges to be flush and straight.

 

I know of another site that has a really informative acrylic thread (on another friendly reef site). It has way more information than you will ever need, but it breaks it down in a manageable way. I can't remember if it is okay to post links to other aquarium forums (I've been away for a while), so if someone confirms it is okay, I'll post a link here.