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Cyanobacteria … or Spirulina algae?

Cyanobacteria is a common occurrence in saltwater aquariums. Aquariums under a year old seem particularly prone to outbreaks.

Cyano is typically red. But it can also be brown, blue-green, or even green.

Regardless of the color, it grows in slimy strands that form  ‘mats’ on the rock and sand.  (To see some great pictures of a typical red cyano out break, check out this page over at Melev’s Reef.)

So, when these green, slimy ‘mats’ began showing up on my rock and then my sand bed a few weeks ago, my first thought was cyanobacteria.

It looked like green cyanobacteria
I thought green-colored cyanobacteria was beginning to cover my ball sponge and sand bed…

However, my online research soon revealed that cyanobacteria has a little-known relative that looks exactly the same to the naked eye: spirulina algae.

And it’s important to know which one you are up against because the methods for treating the two can be quite different.

How can you determine if it’s cyanobacteria or spirulina algae?

Simple, with a few drops of hydrogen peroxide.

Chances are you already have a bottle sitting in your medicine cabinet. If not, you can pick up a regular bottle of 3% hydrogen peroxide at most any grocery store or corner pharmacy.

Simply place a few clumps of the cyano into a container along with 2 cups of water from your aquarium.

Add 1 ml (20 drops) of hydrogen peroxide to it and then let it sit for several hours.

Peroxide is deadly to cyanobacteria. It easily breaks the cyano down and kills it. But peroxide has absolutely NO effect on spirulina algae.


If the water turns the same color as the cyano, it means you are indeed up against cyanobacteria.

If the water remains clear and the ‘cyano’ clumps show absolutely no signs of dissolving, then it is NOT cyanobacteria.

There are several methods you can use to get rid of cyano.

Many aquarists use the old-school method of keeping their tank lights off and the entire room dim for 3 days in order to starve it of light.

In some cases this isn’t enough to do the trick though and the cyano returns a few days after the lights are turned back on.

Others recommend dosing the aquarium with peroxide using a dosage of 1 ml of peroxide for every 10 gallons of water twice per day for 14 days straight.

Mild doses of peroxide have been proven to wipe out cyano while being safe on all other tank inhabitants.

And still others swear by the use of products like ChemiClean and Red Slime Stain Remover.

In fact, Chemiclean will eliminate both cyanobacteria and spirulina.

From what I’ve read, the key to success with products like these is to follow the direction to the tee. That means making sure you oxygenate the water as much as possible with powerheads and/or air stones. And doing the recommended water change as soon as the treatment is complete.

As for me, well, the water in my test stayed clear so it’s not cyano. That means it’s either spirulina or some other form of algae.

I’m going to give my tank a few more weeks to see if regular water changes will lower my nutrient levels enough to both starve it out and bring my good bacteria back into balance with the bad bacteria.

If so, the outbreak I’m experiencing may clear up on it’s own.

If it doesn’t, I’ll probably pay a visit and order some Chemiclean.

Hydor Slim Skim Nano Skimmer Review

The Hydor Slim Skim Nano is one of the slightly larger and more affordable nano skimmers currently available.

Some seasoned aquarists feel it isn’t worth spending money on a skimmer for a nano aquarium. They believe nano skimmers are too small to create enough micro bubbles to pull out a significant amount of organic waste out of the water.

Instead they feel it is better to simply rely on water changes and put the money into coral, fish or something more enjoyable instead.

For the first 6 months of running my tank, I followed this advice. I would change out 4.5 gallons of water (a 20% water change) which would bring my nitrates down to about 12ppm. Then two weeks later they would be back up around 20-24ppm – at which point I would do another 20% water change.

Then I decided to try a skimmer.

I chose the Hydor Slim Skim Nano.

It was rated for aquariums up to 35 gallons – my nano is 24 gallons. And its dimensions fit the first chamber of my sump really well.

I’ve been running the Hydor Slim Skim Nano for 6 months now.

Here are my experiences with it so far:

Pros of the Hydor Slim Skim Nano:

  1. It has kept my nutrient levels much more stable. I am no longer seeing swings from 12 ppm to 24 ppm of nitrate between water changes. After adding it I only saw a swing of about 4 ppm between water changes. This was with no other mechanical filtration other than the Slim Skim Nano.
  2. This skimmer combined with the use of filter floss – has helped bring my nitrates down to 8ppm – and has allowed me to switch to smaller, weekly water changes of 10% (just 2 gallons) while keeping my nitrates around 8ppm without much of a swing in between.
  3. It is nearly silent other than a very slight hum – a great bonus considering my aquarium is in my home office where I work.
  4. The collection cup is easy to adjust, and easy to remove when it needs to be emptied.
  5. It’s magnetic suction cup mounts allow it to be set up in any aquarium or sump with a water depth of 10″ or more.
  6. It is quick and easy to disassemble and clean.
  7. It’s affordable.  The Hydor Slim Skim Nano is one of the least expensive nano skimmers on currently available.

Cons of the Hydor Slim Skim Nano Skimmer:

  1. While it did help to hold my nitrate levels steady, it did not help to continually lower them on its own. I had to add a second form of mechanical filtration – in this case, filter floss – to bring levels down. Perhaps some of those more experienced aquarists are right – nano skimmers may be too small to clean a ‘dirty’ tank on their own. They may best for maintaining low nutrient levels in an already ‘clean’ tank.
  2. The Hydor Slim Skim draws it’s air from inside the skim-mate collection cup rather than outside like some other skimmers (I haven’t yet figured out why…). When the cup is filled with a lot of foam, some of that moisture gets pulled into the air tube. As a result, the tube need to be blown out or cleaned out every few weeks or it may become blocked.
  3. The o-ring on the collection slides only has a slightly snug fit. This is both good and intentional as it allows for easy adjustment of the cup height. However, if you press too hard when putting the lid and air valve back on after emptying the cup, it will push the cup down and move it out of adjustment.

Here are a few shots of the skimmer in action:

Hydor Slim Skim water level for best skimming
Proper water level on Hydro Slim Skim Nano.

I’ve found the Hydor Slim Skim Nano works best for me when the waterline is between halfway and three-quarters of the way above the bottom of the entry slits.

The black rubber o-ring around the collection cup can be adjusted up or down depending on the bio-load of your tank.

If you have a lot of fish and critters start out with the ring closer to the bottom of the cup.

If you have a light bio-load start out with it closer to the top.

Every few days, adjust it a quarter of an inch up or down until you are producing the darkest skim-mate possible.

The best I’ve gotten it so far is the color of very dark tea.

Skim-mate produced by Hydor Slim Skim Nano
Skim-mate looks like dark tea.

More information on the Hydor Slim Skim Nano can be found at the Hydor USA website.

3 Popular Ways to Acclimate Saltwater Fish

There are three popular ways to acclimate saltwater fish: ‘QT Matching’, drip acclimating, and float acclimating.

Each one will work, but some can be more dangerous to your new fish than others.

Let’s take a look when you should use each one and why.

Three Ways to Acclimate Saltwater Fish:

1) Quarantine Matching

Quarantine Matching may well be the safest way to acclimate saltwater fish.

What exactly is ‘quarantine matching’? Simple.  It’s matching the salinity and temperature of your quarantine tank to the salinity and temperature of the water in the bag or container your new fish arrived in.

It can be done quickly and easily. And it allows you move the fish out of the dirty water it came in as quickly, and with as little stress, as possible.

Of course, this method will only work if you have a quarantine tank and the ability to quickly change it’s salinity.

If you already have other fish in your QT tank and therefore cannot quickly change its salinity to match the transport water your fish arrived in… or, like me, do not have a QT tank, then method no. 2 is your next option.

2) Drip Acclimating

While not ideal, many aquarists consider this to be the second safest way to acclimate saltwater fish.

Drip acclimation involves placing your new fish – and the water it came in – into a small container. Then slowly dripping water from the tank they will be housed into that container.

For example, in this image you can see the narrow length of tubing I used to drip water from my display tank into the container of newly arrived fish.

Set-up used to drip acclimate saltwater fish
The Set-Up I Use to Drip Acclimate Saltwater Fish

The benefit of this method is that is does allow the fish to adjust at least somewhat to the temperature and salinity of the tank they are going to be put in at smooth, steady rate.

I say ‘somewhat’ because it can take fish a couple of days to adjust to a large change in salinity. The drip method will at least give them a good head start.

The danger of this method has to do with ammonia build up…

When fish spend several hours in a small, sealed bag of water, the simple act of breathing causes a lot of non-toxic ammonia to build up in the water.

And when the bag is opened and exposed to fresh air, that ammonia essential begins to oxidize and turn into a toxic form of ammonia that will kill the fish.

If you purchase your fish at a local fish store, this likely won’t be a problem.

However, it can be a very dangerous issue if you ordered your fish online and they were shipped overnight.

Fortunately, there are a couple of ways to prevent the ammonia build up from harming your fish.

You can see the full details – including step-by-step instructions – in this article: How to Drip Acclimate Saltwater Fish.

Now, let’s take a look at third option you can use to acclimate saltwater fish.

3) Float Acclimation

Float acclimation requires the least amount of equipment. But it can also be the most tedious type of acclimation.

Why? Because it requires you to remain right next to your tank for upwards of 45 minutes with no break.

Add in the fact that it also poses the most risk to your display tank and you’ll quickly see why it is the method least used by experienced aquarists.

That doesn’t mean it’s a ‘bad’ method. It just means you need to be aware of the risks it entails.

First, you will be floating the open bag containing your fish IN your display tank. That means you run the risk of spilling a large volume of foreign water into it. If there are any fish parasites or other ‘nasties’ in the shipping water, a spill will release them into your display tank. (At least with the drip method above, the only parasite risk you have is with any that are already on (or in) the fish, not those that are in the water itself.)

The float method also involves pouring about 1/2 cup of tank water into the floating bag every 4 minutes. This means you will have to spend 30 to 45 minutes standing next to your tank.

If you’d like to see the step-by-step procedure for float acclimating your fish, you’ll find an excellent guide on the LiveAquaria website right here.

Those are the overall pros and cons of each method. Hopefully you now have a better idea of which one will work best for you.