Marine Tank Rebuild (100L Tank + Sump)

Had my current marine setup for over a year now, and it’s time to neaten it up. My wallpaper is pealing, and due to all the overhanging equipment, I get a lot of salt damp behind the tank as the salt drys and flakes off.

In this article, I have an operating marine tank with sump already setup. I am moving this into a bigger tank, retaining the sump, and implementing plumbing via drilled holes. I am moving from an open top tank, to fully sealed.

Time for a fully seal tank, with holes cut into the tank for plumbing…

The first task to to ebay a suitable sized tank. I was going to buy one new, but it was a lot more cost effective to find a good condition second hand tank. They are at least half the price. I picked mine up for $150 including stand.

First step was to clean the tank and scrub down any algae that had formed and dried. Use a wet green kitchen scourer for this, as the extra coarseness helps remove the algae as a breeze.

Before drilling, you will need to purchase some plumbing fittings for the tank. What most people use are raintank fittings. If you go down to the hardware store, you will see a selection of raintank fittings. It has a tube with two round pieces of rubber (often called a threaded bulkhead).

Make sure you buy two sizes, a bigger and small. The bigger will be the dump pipe, where water will flow out of the tank into the sump. The smaller will be the return, where you sump pump will push the water back into the tank. Make sure the return bulkhead supports tubing which will fit your current sump pump.

 The dump pipe needs to be bigger, because it is gravity fed, and will always flow slower than a pressure fed pipe (ie. driven by the sump pump). Therefore, you are trying to offset this by using a bigger dump pipe. In my case, dump was 20mm, and return was 15mm. Even with this sizing, you will still need to restrict the flow of the return. More later…

I then organised for holes to be drilled into the tank. My holes were 30mm wide, which easily accomodated both the 20mm and 15mm bulkheads. I took them to a tank builder to have them drilled. You can attempt to drill it yourself, but you will need to ebay the proper diamond hole cutters to do this. You will also need some skill in order to these holes, even with the tools. There are many youtube videos on this, and you should test drill on scrap glass before attempting on your tank. You only get one chance!

When drilling the holes, it is best to have one hole slightly lower than the other. This will be the dump should be the lower hole, and the return should be the upper. The middle horizontal line that you can imagine between these two holes, will be your desired water level.

Next stage is the fun part. You will now pick a background colour for your tank. You can use wallpaper, but you will be disappointed with it in 6 months, when it starts to peel. No matter how well you stick the wallpaper to the glass, it will eventually peel. Spraying also gives a much flatter and consistent background.

For a marine tank, you are unlikely to use decorated wallpaper (plants etc), which is even more reason to just spray it. It is hard to spray the back of the tank once your fish are in it, so make your decision now. I chose to spray my tank blue. Black is another popular colour. Although the bulkheads are black, it is fairly camouflaged. See pics.

You now need to mask up the tank with newspaper. Make sure you cover the opening, as you do not want overspray floating into your tank. As most people will be spraying outside, make sure you do it in an area where there are not too many flies/insects, leaves falling from trees, and where birds might feel the need to rest on your beautiful paintwork. I ran into all of the above, so just a handy tip. Corrective spraying is something you want to reduce.

To properly give good consistency, ensure you face the side of the tank you are spraying towards good light, then look inside the tank and you should be able to see any inconsistency. You will need at least 5 coats of paint. Do not rush this. Ideally, leave at least 30mins between each coat.

Move it to a safe location for it to dry. I left my tank for 3 days to dry.

Once you’ve checked over the paintwork and you’re happy with it, tear off all the newspaper. Now we will test fill the tank and ensure there are no leaks. Put the tank on the proper stand or on a flat surface, with the foam cushioning before filling. The weight of the tank is huge when water is filled. The tank must be on a flat surface, or the tank will crack under filling. Additionally, the foam cushioning helps absorb any bits of dirt or sand between the bottom of the glass and the stand. Without it, a small rock caught under the tank, may cause the tank to crack once the tank is filled with water (remember equal and opposite forces).

If the tank is free from leaks, syphon the water out. The tank is now ready to be used. If there were leaks, you’ll need to patch up the leaks with silicon. Silicon takes at least 24 hours to dry properly. Test fill again after.

Moving everything from one tank to another is fairly big job. Here’s what I did:

  • Get your new tank into position. If you want your new tank in the same spot as your old, you will need to lighten the old tank before trying to move it. Read on.
  • Turn off all equipment for your old tank.
  • Disconnect the sump
  • Connect the new tank to the sump
  • Fill up buckets with water syphoned from the current tank. Have enough buckets to house all your liverock and coral.
  • Place all coral and liverock into buckets
  • Put your fish into the buckets with the liverock and coral. Seperate your fish, as they might not be too happy sharing a small bucket with a fellow mate.
  • Hopefully, your old tank is light enough to move. If not syphon out more water into buckets.
  • If your new tank is same or larger than your old, you may want to reuse all your existing water. This will keep all your coral and fish happy, and help with the climitisation.
  • Shovel out the sand, and put this into the new tank. You may not be able to get all the sand, so you can top up with some extra sand in the new tank.
  • Start filling the tank with water, and place the liverock and coral in the tank. Continue to fill up with water.
  • Return the fish into the new tank, and wait for the sand to settle a bit.
  • Turn on all equipment, and top up the water to ensure the dump and return lines are flowing well.

You should be all done from here!

Update – 5/12/2010

Due to the increased tank size, I’ve had to install a new powerhead. The powerhead is rated at 3000L/hr. Sounds excessive for a 100L tank, but it’s actually just right! No tsunami’s in the tank!

Update – May 2011 More rock!