30 gal frag tank

Written by

fragtank038

A step by step description on how to build a DIY frag tank.

Ok so we wanted to build our own frag tank to go next to our main display. We don’t have quite enough lighting on our main to do most sps’s the right way so a frag tank seemed interesting and a good learning experience as we have just started keeping corals the last couple months. So here is the build with plenty of pictures.

Before i get started i need to send out a big thanks to Ziggy953 and marc from Melevsreef.com – Welcome!. without their guidance and help this project never would have gotten of the ground. Thanks guys.

Also we researched how to work with acrylic and based our design off of information on melevsreef so if there are things I’m missing it’s all there in great detail.

So this is what we started with. 2x 24″x48″x 1/4 and one 12″x24″x 1/16 sheets of acrylic.

These are all the things we started out with. We also used a 10″ table saw, router table, cordless drill, and a miter saw. There are a few other random things but nothing big and you can fill in the blanks.

So next step was to lay out all the parts and such which we had done before purchasing the acrylic to make sure we had enough material. I just drew it up in paint to help me visualize it and double check i wasn’t screwing things up.

The smaller 1/16 sheet was just for the box that goes around the plumbing. Next step was to go out and cut out all our pieces. This is where we used the table saw. Marc suggests you use a blade with 80 teeth. We couldn’t find that and grabbed one with 100 teeth and this worked great. One thing I would do differently next time is to make sure to call all the pieces that make up the sides of the box at once with out moving the guide on the table saw. This would ensure that they are all exactly the same hight will I will talk about later. This picture is after we have cut out all the pieces and my brother is taking a sanding block with a fairly fine grade sand paper to smooth all the edges. Make sure you don’t round the edges or corners when your doing this.

Ok so after everything was cut and sanded we layed it back out to check things over. At this point we looked at all our edges and if we had any bad spots we tried to make sure they were on the top edge of the tank that the flange would be glued to since this is and unimportant seam that won’t need to be water tight. We marked all the pieces and figured out how the box was going to fit together. This is kind of an important step since some pieces are cut short to account for the thickness of the acrylic on each side and we didn’t want to glue things together wrong.

So it was time for the first seam. Make sure you have another set of hands around because they really come in handy especially if you’re new to this like we were. We uses the “pins method” as suggested by marc’s site. He has a link on there to a detailed description of how to do this. We used a high E guitar string instead of pins. I highly suggest you take a couple practice runs on some scraps before you jump in. The glue is water thin and difficult to deal with some times. We uses #3 weld on but if you can find it i would go for #4 which dries slower and might make things a little easier. Only take off as much of the brown paper as you need to make the seam so the rest is protected from scratches and glue drips (which there were many of). We used a pair of scissors to cut it back so it didn’t get in the way of the squares when we started gluing.

I had my brother hold the piece steady while i glued and pulled out that guitar strings. Then he would make sure it was square while I checked the pieces were flush with each other and looked over the seam for any large bubbles

Since these are the sides you need to really be careful that the pieces are flush on bottom because this is where you need to glue the bottom of the tank on and a gap would make this seam much harder to do and more likely to leak. When I was saying earlier that i would cut all the sides without moving the guide fence on the table saw, this is where that comes into play. Our pieces were off by maybe 1/32 or so but is made the bottom seam a little annoying to get right. We glued the two short sides on first like this and let them dry for a while before adding the last side.

Once those three pieces were good and dry so we were sure the seams wouldn’t get ruined we flipped the whole thing over onto the last side and finished up the two seams to get all our sides as one piece.

Last we glued the bottom of the tank on and did this seam all at once. I called in my dad to help us on this one because the longer sides would want to bow a little bit and I needed both dad and brother to hold the two sides in place while I went about gluing and checking. Next was to make the top flange on the tank which helps to strengthen the whole thing up and make sure the sides don’t bow out over time. Plus it’s nice to have something to keep it from just being an edge that might get annoying if your arm was leaning up against it while working in the tank. Marc does his flange all in one piece by cutting out the center which really is the better option but our tank was on a budget and we had just enough material. Also, Marc recommends leaving your pieces a little long so that they stick out past the seam a bit and going back and routing them off at the end. (Go to melevsreef.com for clarification) I would suggest doing this if at all possible because it makes gluing much easier and probably improves the overall look of your corners. We did four pieces and glued them together to make a flange and then glue the whole thing onto the tank.

For these seams we had to hang it out over the edge of the table because otherwise the glue goes through and soaks under the pieces leaving you with i big old smear in the flange (which we figured out the hard way). A couple of wood clams do a great job holding the pieces in place while you glue. So after all this we have … a box.

But more importantly we have a box that holds water!!

At this point we took a little break to go to a frag swap which was very interesting (first one) and we ended up picking up quite a few little frags for very cheap (15$) I will probably put up updated pictures of my tank in my other tank journal thread which you should all come and “oohhh ahhhh” at my new corals. But when we got home we had no place to put our new frags so we had to set up my brothers little pico tank he will be taking to school next semester.

The 36″ fixture for the frag tank was a maybe just a little big for this tank. But it did the job till we got things set up. Ok so next we made a stand out of 2×4 with a piece of 3/4 ply wood on top to support the tank. I’m sorry i forget to take pictures of this part but it should be very simple. You can see pictures of it completed in a bit. After this we needed to cut the acrylic for the bulkheads to go through the bottom. A hole saw bit and our cordless drill did the trick but it actually started to melt the acrylic as we were drilling so we needed to pour some water over it as we were going to keep things cooled off. Be sure to leave enough room that the bottom of the bulkhead fittings won’t hit the edges of the stand and you have enough room for your plumbing. Heres things put together with our plumbing just kind sitting in there to show we had enough room with out hitting the sides of the tank.

Next we needed to make the box that goes around the plumbing which required cutting some teeth in the top edges. Marc has a whole page of different ways to do this on his site but we did things just a bit different. We made a jig of sorts to help guide the piece over the router bit. We started by getting a bit that was the width we wanted the teeth and moving the fence on the router table back the depth we wanted the teeth. I think we ended up going 3/8 wide by 1 3/4 deep. The jig consisted of a flat piece of wood with a bar glued on to guild the acrylic up and down the the table.

On the under side we glued another bar that fit into a groove on the router table that would allow the whole jig to move left and right on the table for the different teeth. We would clam the whole jig to the table so it didn’t move while we were cutting each tooth.

It worked quite well and this is what we got when we were done.

Next we took a trip to the hardware store and got all the fittings and pvc to plum the tank back into the sump of our main display. For the drain we used 3/4 pvc and the pressure line was 1/2 flex hose because we had to put the pump in a place that would have been very difficult to plump out of pvc. For the return we made a durso standpipe this helps to keep the plumbing nice and quiet. The pressure line we used some pvc to come up over the top of the box and we have since attached a lock line goose neck fitting that you can get at the LFS so we could direct the flow where we wanted in the tank. Heres the top side of the plumbing.

Notice that we put a piece of 3/4 hard styrofoam under the whole tank. Marc suggests this incase your tank isn’t perfectly square it helps to keep additional pressure off your seams. We took his word for it because we didn’t want 30 gallons on the carpet one day. Another picture sligtly zoomed out.

The underside going into the main cabinet.

Last the plumbing on the inside of the main cabinet dumping out into our sump. The flex hose is just to the right of the return line and we had to stick the pump down to the left of the skimmer which is why we needed the flex hose.

Ok so that about does it. Here are some pictures of everything put together. We will be putting a front on the stand and painting it the same color as the main display cabinet so they match. A little egg crate to hold the frags in the tank and some left over pvc were cut up and used as legs to put the egg crate off the bottom of the tank.

There are a few of the frags we picked up at the swap happy in their new home.

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