Category Archives: How-To’s

Filter Floss: When to Replace It for Optimal Aquarium Health

A common question among new aquarium owners is, “How often should I replace my filter floss?”

And one of the most common answers you’ll see on popular reef keeping forums is “every 2 to 3 days”.

There are two slight problems with this rote piece of advice though:

  1. It could cost you extra money. And,
  2. It could starve your tank.

Every tank is unique, including yours. Just because changing the filter floss every 3 days works best on another person’s tank doesn’t mean it will work best for yours.

How often you change your filter floss will depend on your bio-load and the maturity of your tank.

filter floss cut into strips
Filter floss cut into 1 inch strips for placement between sump baffles.

Consider a new tank that is less than three months old…

Changing the filter floss too often could deprive the bacteria and other microscopic critters of the food they need to develop. This may result in your tank taking longer to mature than usual.

Likewise, changing filter floss too often in a established, mature tank could strip the water of too many nutrients causing the coral to starve.

So where does the common ‘2 to 3 days’ come into play?

As a starting point.

Filter floss isn’t needed until you reach your desired nutrient levels. Phosphate of 0.03 ppm and nitrate of 1 to 5 ppm are most typical.

Once your tank is at your desired nutrient levels begin using filter floss.

For the next 4 to 6 weeks replace it every three days.

Be sure to test your phosphates and nitrates at least twice a week during this period.


Let Your Tank ‘Tell’ You When to Change the Filter Floss

If your nutrients continue to rise during the test period switch to replacing it every 2 days – and consider adding additional filtration such as a skimmer and/or granular activated carbon if you don’t already use them.

If your nutrients hold steady or drop closer to zero during the test period, try replacing the filter floss every five days.

Keep testing for 4 to 6 weeks.

If the nutrients continue to hold stable or drop, bump the replacement schedule out to once a week.

Keep testing. And keep bumping the schedule out.

When your nutrients start to rise a little, stop and switch back to the previous schedule. Congratulations! You’ve found your filter floss replacement ‘sweet spot’.

For example, if they were stable when you replaced the floss every 7 days (once a week) but started to rise when you replaced it every 9 days, stop. 7 days is your replacement ‘sweet spot’.

Changing it more often than 7 days would just be wasting money. And waiting longer than 7 days will cause your nutrient levels to rise.

What if your able to go for several weeks without replacing the floss and still see no rise in your nutrient levels?

Well then you may not need to use filter floss at all. It would indicate the other biological and/or mechanical filtration in your system is more than enough to keep your nutrient levels in check.


A Simple DIY Crab Trap for Catching Aquarium Pests

This DIY crab trap is a quick and easy way to remove unwanted nuisance crabs from your aquarium.

Unwanted pests such as gorilla crabs and stone crabs often make their way into aquariums as hitchhikers on live rock.

At first that my not be a problem. They can even serve as a valuable member of a clean-up crew while they’re small. But as they get bigger and their appetites grow, they will often start to eat corals or other more desirable members of your clean-up crew such as porcelain crabs, snails, and even small fish.

Many aquarists will spend hours trying to spear them with a skewer, or a pair of large tweezers. And some will even resort to spending anywhere from $15 to $50 on a pre-made pest trap.

Before you spend that much time or money though, there is an old reef keepers’ trick you might want to try first.

You can make a very simple DIY crab trap using nothing more than a small glass.

Here you can see the quarter-sized stone crab I caught an ordinary shot glass. Two tries with shrimp didn’t work. But it took less than 30 minutes to catch when I used a little bay scallop as bait.

shot glass crab trap
Small stone crab caught in a DIY shot glass crab trap.

A shot glass will work for small crabs that are about the size of a quarter or smaller.  For larger crabs you can use a bigger glass; one that is just tall enough so that the crab can’t reach the lip if it extends its claw.

The only thing you need other than a glass is some bait. Some people have success with a piece or raw shrimp from the grocery store. I tried shrimp twice but didn’t have much luck with it. On the third attempt to catch the little stone crab that was terrorizing my tank, I tried a small piece of raw bay scallop and it worked like a charm.

Simply place the glass in the bottom of your aquarium about 30 minutes before the lights turn off for the night, and lean it at an angle so the lip of the glass is resting against a rock.

Then place a small piece of the bait in the bottom of the glass and let it sit overnight.

The crab will climb down into the glass to eat the bait. But it won’t be able to get back out because the walls of the glass are too smooth for it climb up.

It make take a few tries, but a lot of reef keepers have had great success using this quick and simple DIY crab trap.


A DIY Nitrate Reactor for Your Aquarium

This DIY nitrate reactor is simple and inexpensive to make – and is great for keeping the nitrates in your aquarium below 2 parts-per-million.

I always struggled with keeping the nitrates in my 24g aquarium any lower than 12 ppm.

Two weeks after making this nitrate reactor, my nitrates fell to 2ppm. And for the past month they have continued to hold steady at 1 to 2 ppm.

Stuff needed to make the nitrate reactor:

  • Seachem De*Nitrate (every 1 liter treats up to 100g of aquarium water)
  • an empty mayonnaise jar with plastic lid (I just bought a cheap $2 bottle of fake mayo at the local grocery store and dumped the contents in the trash) – or any other jar with plastic; just make sure it’s large enough to hold enough De*Nitrate to treat your tank
  • a 1′ piece 1/2″ diameter PVC pipe (Home Depot, Lowes, or most any other local hardware store)
  • a 1/2″ PVC barbed insert x female adapter (FIPT x insert) (you will most likely have to order this online)
  • a 1/2″ PVC spigot x male adapter (Home Depot, Lowes, or most any other local hardware store)
  • a tube of JB Waterweld (Home Depot, Lowes, or most any other local hardware store)

The tools you’ll need to make it:

  • either a hacksaw or coping saw
  • a drill
  • 1/8″ drill bit
  • 1/4″ drill bit
  • 7/8″ drill bit
  • small piece of sandpaper (any grit)

How to assemble it:

  1. Use the 7/8″ drill bit to drill a hole in the center of the mayo jar lid. Lay the lid upside down on a piece of scrap wood to drill it so that pressing down on it with the drill won’t crack the plastic lid.
  2. With the lid still upside down on the scrap wood, use the 1/8″ drill bit to drill several small holes around the outer portion of the top of the lid. (These holes are how water will exit the reactor.)
  3. Use the saw to cut length of PVC pipe equal to the inside height of the jar.
  4. Glue the spigot end of Spigot x Male adapter onto one end of the piece of PVC pipe you just cut.
  5. Trim the opposite end of the PVC pipe just enough so that it is held snugly in place when you stand it in the jar an screw the lid down over the top it:with lid on
  6. Remove the pipe from the jar and use the 1/8″ drill bit to drill several holes in the bottom end of it. (The incoming water will flow down the pipe and then exit the pipe into the bottom of the jar.)
  7. Use sandpaper to remove any burrs from the bottom of the pipe, then use sandpaper to lightly scuff the inside bottom of the jar.
  8. Place some JB Waterweld epoxy on the bottom end of the PVC pipe, then press the bottom of the pipe into the bottom of the jar. Make sure the epoxy has stuck to both the pipe and the jar enough to hold the pipe in place.
  9. Place the lid on the jar so that it hold the pipe centered in place while the epoxy cures overnight.
  10. After the epoxy has fully cured, remove the lid, cover the top of the pipe with your finger, and pour the appropriate amount of Seachem De*Nitrate into the jar.
  11. Replace the lid and screw down until it is just snug.
  12. Screw the Barbed Insert x Female Adapter onto the top of the pipe sticking out of the jar until it is just barely snug.
  13. You are now ready to place it in your sump and attach your water feed to it making certain the flow rate through it will be no more than 50gph.

In my case, I tee’d a 1/2″ line off my main return pump line. And I stuck a cheap 2 Little Fishes Ball Valve in it to control the flow just before it enters the reactor.

I also used the spare space in the jar to hold a bag of granular activitated carbon and another mesh bag with some Seachem Phosguard in it.  That way I can get flow through all three types of filter media without have to use any electric pumps. (The fewer pieces I have to plug into my power strip, the better.)

To replace the Phosguard and carbon, I simply unscrew the barbed fitting, then unscrew the lid.

The De*Nitrate pebbles never need replacing, It is a good idea to rinse them off with clean water every now and then though. That way detritus build up won’t block the microscopic pores the anaerobic bacteria live in, and they can continue consuming the nitrates from your tank water.

Since De*Nitrate requires a flow of 30 to 50 gph to pass through it for optimal performance, I adjusted the ball valve to provide a flow of about 35 gph through the reactor.

Here are some shots of my nitrate reactor setup:

empty nitrate reactor
Empty nitrate reactor


media in reactor
De*Nitrate on the bottom, a bag of carbon and a bag of PhosGuard on top of it.


nitrate reactor in sump
Water flows down to the reactor, down through its center pipe, up through the media, and out the little holes in the lid.


nitrate reactor valve
Water is feed from my return line, though the ball valve, down into the reactor jar.