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New Jersey Scuba Diving


New Jersey Scuba Diving

Aquarium Guide - Tank

Aquarium Guide

Hermit CrabAll aquaria today are constructed of tempered glass, with silicone seals and plastic frames, or entirely of clear acrylic. This is exactly the way they should be constructed, and it is hard to go wrong with a new tank. If possible, you should leak-test a new tank for a few days outside or somewhere where a little dripping water will do no harm, but the incidence of leakers is really very low. If you use cold water, expect condensation all over the glass until it warms. This is not leaking; just dry it off with a towel. Aquarium glass will scratch. You should always be gentle when moving the gravel or stone decorations inside the tank. Acrylic scratches very easily, and for this reason, along with the high cost, I would avoid it.

Black Sea BassThe carrying capacity, or number of fish you can keep in a tank is determined by its size and shape. Obviously, a larger tank will hold more fish, but there is more to it. Oxygen is usually the limiting factor in carrying capacity, and oxygen enters the water at the surface of the aquarium. Therefore it is the surface area of the tank, rather than the overall volume, that really determines how many fish you can keep in it. Because of this, very tall narrow tanks, like some of the hexagonal models, should be avoided.

Water circulation can double or triple the carrying capacity of any fish tank, but only when it is on. If the filter on an overstocked tank fails for any period of time, you could lose some or all of your fish. It is good to have a small air pump as a backup for just such emergencies. This is actually a pretty rare event, and normal down-time for cleaning will do no harm.

Sea RobinYou can find many formulas for calculating just how many fish you can keep in a particular sized tank. These are based on tank dimensions, fish size and type, etc. I routinely stock my tanks to much higher densities than any of these formulas would allow, and the fish suffer not in the least for it. I would say the best formula is experience. Stock your tank slowly, and as long as the fish look happy and healthy, you are OK.

A great deal depends on the personality of the fish you keep. Very active types can drive each other to madness if overcrowded. In other types, their natural territoriality may be magnified by the close quarters to the point that they may become holy terrors, such that anything more than one in a tank is Seahorseovercrowding! This clearly has nothing to do with oxygen levels. Experience is the best guide in this matter, and in any case, go slow. Some indications of overcrowding are: ragged fins, skin lesions, gasping at the surface, weight loss, manic behavior, fetid odors, and death. Not that much different from people.

Large tanks tend to be more stable than small ones, in terms of temperature and water quality. A small tank can go bad very quickly and become a total loss, whereas a large tank will give more warning of such problems. In this way, large tanks are more forgiving. Small tanks should therefore be stocked more lightly than large ones, and if you are just starting out, try to get 20 gallons or more.


Apart from the fish, another major concern with aquaria is weight. For simplicity, I estimate an aquarium weighs 10-11 pounds per gallon. Thus, a 55 gallon aquarium will weigh around 600 pounds. Since this weight is spread out over the area of the tank, it should be well within most floor design specifications. However, over the long term, a wooden floor may begin to sag under this load. To minimize this, try to locate large tanks in corners, or near walls, or above supporting walls in the floor below. Small tanks can be placed on ordinary furniture, but remember 10 gallons = 100 pounds. Anything more than this should be placed on a properly constructed stand.

Baby Cunner

Remember, an aquarium is full of water, and routine activities are bound to spill and splash it around. This can result in water marks and stains, since it is often impossible to move a tank to clean under it. Therefore avoid placing an aquarium on any expensive furniture or carpeting. Also, should a small leak ever develop, anything you keep below the tank could be ruined, so don't put anything valuable there.

SeahorseTanks larger than 20 gallons should never be moved unless completely empty. Tanks 20 gallons and smaller can be moved without breaking them down by draining as much water as possible, and removing heavy objects, like filters, large rocks, etc. You can leave the fish in the tank for short trips, and save the water for refilling in the new location.

While we are here, a word on the all-in-one starter kits you may find in the stores: some of them have pretty good components, most of them do not. If you have a friend who knows the difference, bring him/her/it along. Luckily, the better stuff also costs more, so in this case the salesman will happily steer you in the right direction. Don't start out with junk.


Aww Damn ! Now I'm going to have to look at that forever !

It happens. A glass box full of pebbles ( or worse, sand ) is going to get scratched sometime. Nothing ruins a beautiful aquarium like scratched glass. Fortunately, there is a way to get rid of scratches without having to break down the whole tank and polish them out the conventional way, or replace it. Glass is very hard compared to most materials you would sand, and also transparent, revealing even the smallest imperfections in the light. Ordinarily, sanding glass without heavy polishing afterwards would simply result in an even worse mess of scratches, but we have one thing in our favor here - small enough scratches become invisible in water, and the inside of the tank is always filled with water.

To do this, you will need silicon carbide ( SiC, also known as carborundum ) sandpaper in several grits. Typical wet-or-dry sandpaper is aluminum oxide. This is fine for woodworking, but barely works for this. Silicon carbide is the second hardest material known, after diamond. It has a Mohs hardness of 9.5 ( diamond is 10. ) Glass is around 5.5, your fingernail is 2.5. Although aluminum oxide has a hardness of 9.0, it is not nearly as tough as silicon carbide, and dulls-up against glass literally in seconds. You can find SiC paper at most auto parts stores - it is the stuff in the small package that is inexplicably overpriced. It should say silicone carbide somewhere on the package. That's the reason it is so expensive. You can also find it online, as if I needed to say that.

First, clean the glass on the outside. You don't want to confuse scratches on the inside with streaks on the outside. Then, with a Sharpie pen, circle the scratch you want to remove. Settle for two or three of the worst, don't be overly ambitious, this is a lot of work. I tear the paper into small pieces about 3x4 inches, and then fold those in half.

Attack the scratch first with 800 or 1000-grit sandpaper. You want to use heavy fingertip pressure, switching the contact point of the paper ofter. Keep switching the spot on the paper, and once the whole piece is dull, throw it away and get a new one. Use just your fingertips, and keep the 'over-sand' area to a minimum, checking often to see your progress until you are satisfied with the results. Light scratches come out completely, medium ones take more time and effort. For large deep ones, you may have to be satisfied with whatever you can do, but you should be able to minimize it with enough work. Even just rounding the microscopic edges of the scratch will make it less apparent.

You can attack bigger scratches with 800 or even 600 grit paper, but this will leave behind visible roughness that you will have to remove with 1000, which means even more work. So if at all possible, try to do everything with 1000. You want to see little white wisps of dust floating away, otherwise you are not cutting glass. Feel and listen with the sandpaper - after a few minutes it will lose its 'edge' and slip against the glass without making that scratching sound. That means you need to look for an unworn spot on the paper, or get a new piece.

1000 won't leave visible scratches, but it will leave a slightly hazy or milky spot on the glass that is visible from some angles. You can take this out with 1500 grit. At this point, you can use the 1500 to feel for the rough spots left behind by the 1000. Rub them out, 1500 should return the glass almost to its original smoothness and clarity. You should make a lot of white 'smoke' as you cut down the edges of the 1000 scratches. You could follow that with 2000, but I am satisfied with the results from 1500.

It helps to remove some water from the tank, because this is a wet splashy job. If you have delicate, or nervous jumpy fish, remove them to a bucket. My fish didn't mind the process at all. Sanding releases clouds of carborundum and microscopic glass particles into the water, but this is essentially the same stuff as the quartz gravel you probably have in the tank already. It seems to do the fish no harm, and the filter will clean it up quickly.

If this sounds very laborious, it is. Your hand may cramp after a while, and my fingertips got raw. Don't try to get it done all in one day, take your time. Don't mark out any areas much bigger than 1x2 inches. It is better to do a really good job on one or two spots than to make a mess of the whole tank. Palm-sanding the entire inside surface of the glass will have no noticeable effect, you need to attack each scratch individually. Don't try to conserve sandpaper, this job is hard enough already, and once the paper goes dull, you are accomplishing nothing. Remember - heavy fingertip pressure - it will make the paper last longer, and the job go faster. I also use the side of my thumb, and both hands.

I worked out this process by trial-and-error, starting with polishing papers in the multi-thousands. I was rather surprised to find myself eventually using 400-grit on glass. That was a mistake, it took longer to polish out the 400 marks than to remove the original scratches. But in the end had a like-new tank, without having to break it down. I am more than pleased with the results. Scratches that have irked me for years are now gone. I have to look for the defects to see them now. The nice thing about this method is that you can revisit it whenever you feel like it, just get a piece of sandpaper and go to it. Make the sandpaper part of your aquarium kit.

I don't know how this would work on an acrylic tank. It might be easier ( probably ) or it might be a disaster. They scratch so easily, that's why I've never owned one. I've read a lot of bad advice on the internets about how to do this, most of it involving breaking down the tank and polishing kits that don't work, or simply saying it is impossible. This works, and while it is a lot of work, it is relatively little hassle or cost. The key is getting the right sandpaper, and making a determined effort.

Aquarium Guide - Water

Aquarium Guide


If you can drink it, then your tap water is probably OK to use in your aquarium. This is especially true if the water comes from a municipal supply. If your water comes from a well, this is less certain. There are several factors to consider in water quality: pH, hardness, chlorination, and other chemical contents.

pH is a measure of how acid the water is. The scale runs from 1.0 ( most acid ) to 7.0 ( neutral ) to 14.0 ( most alkaline ). Most freshwater tropical fish prefer slightly acid or neutral water - pH 6.5 - 7.0, although there are notable exceptions. In my town, the pH of tap water is about 8.0, while well water from nearby is closer to 5.0. Fish wastes tend to cause aquarium water to become more acid over time. In my case, the alkalinity of the tap water counteracts this. However, I have seen the well water kill Goldfish! pH test kits are inexpensive and well worth it. There are special chemicals available for treating pH, but I would only use them under extreme circumstances. Generally, the range 6.0 - 8.0 is tolerable for freshwater.

Sea Robin

Hardness describes the amount of dissolved salts in the water. Distilled water is as soft as it can get, while sea water is off the scale in hardness, as far as we are concerned. Again, municipal water is probably not a problem, but well water may be. There are test kits for this also, but I wouldn't bother unless I knew there was a problem. Ask around. Most fish will tolerate a wide range of hardnesses. Most fish will also tolerate a degree of iron in the water as well.


Most saltwater aquarists have no recourse but to make their own saltwater from store-bought salts. This has the advantage of making near-sterile water, but it can also be expensive. If you live near the shore, you might be better off investing in some 5 gallon buckets with lids, especially if you intend to keep local fishes and invertebrates. The easiest place to get clean seawater is from a bulkhead near the mouth of a river, on an incoming high tide. This will be nearly pure clean seawater. It may also be full of plankton, a treat for some aquarium creatures. Unfortunately, there is no telling what else may be in the mix, and you could introduce parasites, viruses, bacteria, and other disease. For wild-caught fishes in good health, this should not be a problem. A good filter will quickly clean up not-quite-clear water.

Saltwater aquaria should be kept at a pH of 8.0-9.0. All aquaria tend to acidity over time. While this is usually not a problem in freshwater, it is death to a marine tank. Crushed coral is the best way to counter this trend and keep the pH buffered in the correct range. See the section on filters for a great way to incorporate this material in your aquarium filter.

hydrometerLocal seawater has a specific gravity of about 1.022 for full ocean salinity, down to around 1.015 for brackish water. In any case, a good quality hydrometer will be needed to determine the salinity of the water. The Marineland model at right is widely regarded as accurate for aquarium use, and is also inexpensive, easy to use, and can be taken into the field. Float-type hydrometers should be avoided, as inexpensive models are seldom usefully calibrated or accurate, and are also fragile and bothersome to use.

For a fish-only aquarium, reducing the salinity below full-ocean levels can be advantageous. Many of the fishes you will collect will come from such brackish environments in the first place. Reduced salinity reduces osmotic stress on the fishes, improves oxygenation, kills many pests and parasites directly, and eases many of the chemical and biological difficulties inherent in a marine aquarium. Most crustaceans, starfish, anemones, and other invertebrates can also handle brackish water, but urchins cannot.

Water Changes

Regular partial water changes are just as essential as filtration. Water changes remove harmful proteins, salts, and chemicals that the filter will not. They also replenish trace minerals and mediate pH levels in the tank. Many fish benefit directly from just the change, which can be thought of as simulating a rainfall or natural water flow. Simply refilling the tank as the water evaporates is not the same, as this causes chemicals to build up in the water. Water changes should be 15-20% every one or two weeks.

The best thing for getting water out of a tank is a siphon with a flared end, like the kind any pet store will sell. While siphoning, you can jab the big end of the siphon down into the gravel, and vacuum it out. Its amazing, all the tiny critters that live down there, that you never thought were there. Don't worry, though, they don't do any harm, and may actually be eaten by the fish. Just be careful if you have any fish that like to bury themselves, they could be injured.

Naked Goby

For freshwater, ordinary tap water can be used for replacement, provided the temperature is equal to or slightly lower than the tank temperature, and the pH of your local tap water is not too extreme. Chlorine is not a problem at these levels, and I don't recommend the de-chlorinating chemical that your local pet store will try to sell you. If larger water changes are needed, you should age the water for at least 6 hours or so in non-metallic containers with large open surface areas, i.e. - buckets, not milk jugs. This will allow the chlorine to escape, and some oxygen to dissolve. An air stone will speed the process if you have an extra one. Periodic stirring will also help. Just prior to using it, you can adjust the temperature by adding small amounts of very hot water or ice and stirring. If possible, siphon the replacement water back into the tank, otherwise pour it in slowly and carefully.

For saltwater, the process is similar, with the addition of aquarium salts. Use your hydrometer to match the salinity of the tank, unless you are deliberately trying to change it. Alternatively, if you started out with natural seawater, you can just go get more, and use that. I try to keep several buckets on reserve. For brackish water, seawater can be diluted with tapwater before adding to the tank.

Water Treatments & Test Kits

In general, I do not believe in water treatment chemicals. The aquarium industry thrives by selling these sorts of things, and the times I have tried any of them, they did not fix the problem. If you have water problems, try a water change before trying any additive. Most water problems come from overcrowding - try removing some fish. The only exception is plain old aquarium salt, which is naturally occurring anyway. Don't use iodized table salt, however, that's poisonous to fish ( figure, they have to live in it ). The only other product that I use is Acurel F. This product is pretty effective at clearing that whitish cloudy water in new tanks, but if you need it after that, then there is something else wrong.

There are many water chemistry test kits available. The most common ones are: pH ( several ranges ) freshwater hardness, nitrate, nitrite, and ammonium. Of these, the pH test is essential; the rest are of doubtful usefulness. I have little faith in the accuracy of the low-end inexpensive test kits, and little belief in the necessity of the high-end expensive kits. For a saltwater tank, you will need a device to measure salinity or specific gravity.

Use Your Nose

One of the best ways to judge the water quality and health of an established aquarium is to use you nose and smell it. A healthy freshwater aquarium should have no smell, or a slight earthy smell, like potting soil. Any rotten or sewage-like smell is a sign of trouble - do a 10-20% water change immediately, and look for the cause - uneaten food, a dead fish in a corner, fouled gravel, etc. Continue daily water changes until the bad smell goes away.

Likewise, a healthy saltwater tank should smell like the ocean surf - slightly salty but clean. Any strong, foul, or muddy smell is a sign of trouble - treat as above. If you live near the shore, you could think of this as the difference between a nice salt spray smell at the beach and a low tide smell on a mud flat. Check the odor of your aquarium daily - it's the cheapest and easiest water quality test there is!



I make no claim as to the accuracy, validity, or appropriateness of any information found in this website. I will not be responsible for the consequences of any action that is based upon information found here. Scuba diving is an adventure sport, and as always, you alone are responsible for your own safety and well being.

Copyright © 1996-2016 Rich Galiano
unless otherwise noted



since 2016-09-11