The Hydrometer

Aquarists can use a small arsenal of tests to assure themselves that the seawater quality in their fish only aquariums or reef aquariums is high enough. One of these tests is carried out using a hydrometer.

The hydrometer measures the Specific Gravity (SG) of seawater. SG is the measurement method used overall in the hobby, though more scientific circles could well measure in parts per thousand (ppt).

The hydrometer is a very simple piece of equipment and very easily obtainable for a reasonable price. It comes in two main types, the ‘swing needle’ and ‘floating needle.’ Both types are suitable for a marine aquarist.

The ‘swing needle’ type is usually a plastic box about four inches square, which is very narrow in width and marked with graduations on one side. Inside the box is a needle that can swing in a vertical direction. When the unit is filled with seawater the needle moves and indicates the SG.

The potential problem with these type hydrometers is that small bubbles could be attached to the needle and not be noticed by the aquarist. This will cause the reading to be incorrect. All that is needed is for the aquarist to gently tap the needle with a pencil of similar a few times and any bubbles will be dislodged.

The ’floating needle’ type consists of a cylinder, made of plastic or glass, and a narrow needle which is marked along its length. The cylinder is filled with the seawater to be tested, and the needle is floated inside the cylinder. The needle will float at a certain position, and the aquarist can read off the SG.

The potential problem with this type is that the aquarist will read the needle float point at an angle, and thus an incorrect reading will be obtained. So obviously it is important that the aquarist has his/her eye level with the top of the seawater in the cylinder.

Hydrometers that are specially manufactured for aquarium use are preset for warm temperatures, usually 75 deg F. This is because temperature affects the reading. Aquarist may keep their seawater at a different temperature to this, so the manufacturers often put in a chart to permit an easy adjustment of the reading to be made. These adjustments are often shown in marine aquarium books. However, there is no need to be overly concerned – what the marine aquarist is aiming for is stability, and if the reading of seawater at, say, 77 deg F is the same each week then there is little to worry about.

Another important point about hydrometers is that they must be kept clean to avoid salt deposits that could cause an incorrect reading. This is easily done – with the ‘swing needle’ simply fill it with tap water after use and leave for an hour or so, then empty and leave it to air dry. The ‘floating needle’ type can be the same – fill the cylinder above the level the seawater reached with tap water and let the needle float (it will not be supported by tap water) for an hour or so, then empty it out and dry with a clean cloth.

If I had to pick one of the two types of hydrometer, though there is not much to choose between them, I would go for the ’swing needle’ type. This is because it is probably a little easier to use and, at least in the case of glass, stronger than the ’floating needle’ type.

A hydrometer is an essential piece of equipment and every marine aquarist should have one. Specific Gravity should be tested at least weekly, and should certainly be in the aquarist’s testing routine.

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Aquarium Lighting Advance

In years gone by aquarists lit their aquariums with tungsten lights. They probably had no idea of spectrum, probably had lots of algae growth, and I would imagine the heat output would have caused problems too. Methods advance.

Nowadays there are two main lighting systems, fluorescent tubes and metal halide bulbs. Fluorescent tubes are mainly used for fish only and soft coral systems, with metal halides lighting mostly hard coral reef systems.

Aquarists have a wide choice of tubes and bulbs, with spectrum being tailored to need. One major ‘fault’ is that to achieve high power output, that is, use metal halide bulbs, there is a premium to pay for electricity. In addition, nowadays we are more aware of our carbon footprint, with all the concern about global warming that has arisen.

Well, the ‘advance’ I’m writing about is not exactly new. I’ve written about it before at some length. The lights are LED’s, which up to now (as far as I am aware) have been available in two forms – moonlight low power and full lighting high power types. It is the high power types that have ‘advanced’.

Up to now the only LED lighting available to light a reef are full arrays, where a high number of LED’s are inbuilt, with different colours incorporated. These arrays come in different sizes for different size aquariums. Trouble is, they are very expensive despite the many advantages they offer (see under Articles and under the sub-heading Equipment – ‘LED Lighting’).

The advance is not so much in technology (as far as I know) but in choice. Power LED’s are coming on to the market which offer choice in much the same way as fluorescent tubes do.

The units which, as said, resemble a fluorescent tube, are a little under 20″ (circa 51cm) in length. They each have 5 LED bulbs and can be obtained as full spectrum, natural daylight, marine white, reef white, marine blue and reef blue. I am not aware at the moment what the difference is between ’marine’ and ’reef’ in the white and the blue. Perhaps one of the blues is the actinic equivalent?

Anyway, with LED’s the aquarist can now ’mix and match’ according to need.

The big drawback, as before, is cost. I understand the light ’tubes’ individually will cost around $175. Ouch! This is tempered however by the cost of running them, which could be as low as around $15 per annum. The lights run at 12v DC. The bulbs are said to last about 50000 hours! The heat output is reported to be very low, so further savings might be made on the cost of a chiller.

The only power output indication I’ve managed to discover is that at 50cm from the aquarium, the LED ’tube’ produces around 33% more light than a 24W compact fluorescent. Fluorescents are usually much closer to the water surface than that, but at a closer point the ratios would remain the same.

I’m hoping for more information particularly on power output. I don’t know if the lights will challenge the supremacy of metal halides yet, maybe the light output close to the water surface will be something like a lower powered metal halide positioned much higher? Hmm. Maybe?

The exciting point is that the LED is still developing and slowly presenting a bigger choice to the aquarist. If the LED now, or does eventually, offer flexible lighting fully suitable to the varied needs of aquarists particularly those with reefs, then metal halides, considering the running cost and heat output, will no longer dominate. Definitely so if the LED price falls somewhat.

I feel fairly certain that in the course of time LED’s will be the light of choice, particularly for reefs, with all the advantages, especially those of running cost and lack of heat into the aquarium. Power output is the thing for the reef – that will come if it isn‘t here already.

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At What Times Should The Lighting Be On Above The Refugium

In the refugium we are attempting to grow macro algae. The reason for this is that as they grow they remove nutrients like nitrate and phosphate out of the water.

In a previous post I have discussed what type of lighting should be used so that you can get optimum algae growth plus I have also talked briefly about harvesting the algae from time to time.

One thing which I have not really touched upon is how long you should provide lighting for.

There are two methods available – one which I agree with and one which I don’t.

I shall cover the one that I don’t agree with first.

Option 1 – Provide Lighting Over a 24 Hour Period.

So why don’t I agree with this?

Basically it’s because it does not happen in nature. There are some aquarists who believe that providing lighting over a 24 hour period prevents algae crashes from happening. This is where all the algae suddenly dies and all the nutrients which are removed are released back into the aquarium.

To me this has never been proven. If you look at nature the algae beds in the sea are exposed to sunlight over a determined length of time. The same as provided for the corals. You would not leave your lights on for 24 hours to provide light for the corals so why do it for the algae.

I am firmly of the opinion that we should attempt to replicate nature wherever we can. It works in nature so why try to change it in our aquariums?

I also believe that the algae needs a rest!

There is another factor to this as well. This is that in darkness the micro organisms come out more and start to feed and reproduce. It has been noted by many aquarists that they have experienced a pod explosion when the lights are out for a length of time.

Option 2 – Provide Lighting Over A Shorter Period.

This is my preferred option.

I have covered some of the reasons above. i.e. lighting is not provided over a 24 hour period in nature so why do it in our aquariums and the factor of the little critters which we are providing refuge to.

So how long is a shorter period. Well it can be many things but the method I use is that the lights above the refugium turn on when the main lighting turns off above the display aquarium – i.e. the metal halide lighting. They stay on all night and turn off when the metal halides turn on the next day. This is sometimes called reverse sunlight lighting.

So why do I do it this way and not have them on at the same time as the metal halides?

Basically this is so that I do not experience a drop in pH over the nightime hours. The reason this happens is that when the lights are on photosynthesis occurs, carbon dioxide is used and oxygen given off into the aquarium and the pH rises or in this case remains stable.

Stability as we all know is a major factor we are all hoping to achieve.

If we had the refugium lights on at the same time as the main display aquarium when all the lights went off there is a possibility that the pH will drop.

So that’s why I prefer option 2 – it simply makes sense to me.

Another thing that I also do is occasionally turn off the lighting above the refugium for a couple of days. I have found that when I do this I get a lot more ‘critters’ in the refugium. The more ‘critters’ there are the happier I am!

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The Fish Tank Hood – Keep It Cool

There are many aspects in the aquarium which generate heat. There are pumps, heaters and of course the lighting.

The choice of lighting normally determines if you will actually use a hood or not. If you choose to use fluorescent tubes then quite likely you will implement a hood or canopy as they are sometimes known. An aquarium hood may be used with metal halide lighting, however this will probably be determined by the choice of metal halide. If you elect for a pendant type then you may not use a hood, however if you use another type of metal halide then you may choose to use one.

As we all know heat rises and if a hood is chosen then all the heat which is generated by the various aquarium equipment will build up in the hood and therefore could have a detrimental effect on the water temperature. Something we dont want to happen is an increase (or decrease) in water temperature. If the heat builds up in the hood then you will also experience a higher level of water evaporation which could mean fluctuations in salinity plus you could experience an electrical failure due to the elevated heat levels.

The good thing is that it is really easy to rectify.

What you can do (and this is one solution out of many) is install fans into the aquarium hood.

Small fans will suffice and could be installed in both sides of the hood. The fans on the left could be installed to blow cool air from the room into the hood and the fans at the other end installed the other way around so that they are blowing air out of the hood. This way you will get an ever moving flow of cool air through the hood.

There are some people who drill holes in the hood rear or top. Whilst this does remove some of the heat I personally do not believe that this will allow for the heat inside the hood to cool down quick enough – unless the holes are of a large size. I personally believe that there needs to be cool air drawn into the hood.

The ambient temperature of the room also needs to be taken into consideration. If it is a hot day for example then the air surrounding the aquarium will be warm and unless you have invested in an aquarium chiller then probably you are going to struggle to maintain the heat within the aquarium. In these instances if you do not have a chiller it is probably best to remove the top from the hood to allow some of the hot air to escape.

Not always possible though is it as you are not always at home.

Computer fans in my opinion are a good option to use as they are cheap to purchase and easy to install, however there are many other fans which can be used. What you need to look at is how you are going to power them. I suppose an interesting way to do this would be via the use of solar power. This way you could use the lighting as the source of power. When the lights are on the fans are activated and when the lights turn off the fans turn off. Perhaps solar powered fans from a greenhouse could work.

Of course another way would be to just hook them up to the power outlet!

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How To Level An Aquarium Stand

Ensuring that the aquarium is level is important. Sometimes if it is slightly out of level it doesn’t matter as the water surface is often above the lowest part of the aquarium hood, or there is a black band on the aquarium to hide the water surface. If the water level can be seen it needs to be visually correct, and in any case it is best if the stand is level in any circumstance for support.

There are two approaches to levelling, and this depends on the start point of the construction – is the stand being constructed from the start or has the stand been purchased complete.

If the aquarium stand is being constructed, then consideration should be given to the site it is to be used in. Using string or similar, mark accurate lines exactly where the stand will go. Then, using a reasonably long bubble level, lay the level carefully along the string, first along the front edge and then along the end line. (If the level is not as long as the line, use a piece of wood the length of the line and put the level on that. Ensure that the wood is absolutely straight, and not warped at all.) Note in each case if the bubble is exactly in the middle. If it is not, raise the level until it is. A measurement can now be taken of the distance that the level had to be lifted to achieve true horizontal. The same should be done with the side lines.

If the levels of the floor are true, then no problem. If not, then proceed in one of two ways. When constructing the stand, allow the additional measurement to be added to the height of the stand at the necessary end, ensuring that strength and stability are maintained. Properly done, the stand top will be level. Or, second, construct the stand as normal as though the floor was level. Then construct a filler, the thickness of which should be the amount by which the level had to be raised to make it truly horizontal.

The downside of adjusting the stand itself is that if it were to be moved to a new location, then it is not going to be level, and fillers are going to be needed. On this basis, it is best to construct the stand normally, and use fillers as described above. If inserting a filler, make it so that support is given to as much of the stand as possible. It may be necessary, if a floor slopes, to construct a triangular shaped filler.

If the stand is ready built, then use fillers where necessary as described above, after checking with a bubble level in the same way.

Aquariums full of water and rocks are very heavy and need to be stable. This is one of the reasons why the stand is levelled, as well as it being visually correct. Maximum and effective support is required if the floor area is out of true. Hopefully, most floors will be level. A little off topic, make sure that the floor itself is strong enough to support the aquarium. If in any doubt, seek qualified advice.

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