Apart from the 3 new Terences, the rest of the population of the big tank are old hands, and I've had some of them for well over a year. Of course, population and numbers vary, as fish do have a habit of dying. But they all seem happy enough. The corys are catfish, and are very sweet. They're bottom feeders, and, though they do flap around a lot, are happiest sitting on the bottom, waiting for feeding time. The shrimps, inch-long transparent chaps, are gorgeous. Quite bold, will nibble odd bits of debris off a resting cory, but are at their funniest at feeding time, when, if they can, they'll steal a whole algae wafer one eighth of an incg wide, hide, and eat it all. The sucker mouths are very independent, and don't need their friends at all. Usually to be seen with their sucker mouths (underneath their body) attached to some object, they rarely swim, at least not freely in clear water, but will rapidly flap from one ornament or glass wall to another. Elephant snails are quite large (over an inch) snails which wander around on the gravel, or occasionally up the glass. With their 'facial' features, including a trunk, they really do look like elephants. The four neons stick together, mostly, but one, who is of a slightly paler colouration, will sometimes wander off alone. Zebras wander rapidly back and forth near the surface. Friendly, sweet and inquisitive, they're classed as hardy, and make ideal inhabitants of a new perhaps not yet thoroughly settled, aquarium. The two plecos came from my son, who felt that the female, who is orange, was a bit naughty towards his other fish, though she's been fine here. The male, smaller, black, totally adores her, and follows her everywhere, and is rarely more than an inch away from her. Of all of them I only really know the gender of these two. Sexing fish is NOT easy.

So there's a very quick rundown on the guys. What I want to stress is that fish are not just fish - all have very definite personalities and habits. But at the same time, a tank is not just a tank. My small tank took 8 whole weeks to prepare before it was suitable to receive its fish. Yes, 8 weeks. Why? Read on.

Crucial Requirements Explained
As I said above, fishkeeping is not just a matter of slopping some tap water in the tank and sticking the fishies in it. Like any living creature they have strict and important requirements regarding their environment. These are the facts:

1. Warmth - unless you want to keep boring old coldwater goldfish, and, like most of us, want to go the tropical route, then warmth. Tropicals need their water temperatures to be around the 23° to 25° centigrade mark. To achieve and maintain this you'll need a heater. This will take the form of a test tube type of object, with the heating elements inside it. On top there's an adjustment dial and a mains electricity wire coming out of it. It's all completely waterproof, and should be fully submerged. You can add a cheap thermometer into the equation if you want to keep anyeye on it
2. Tap water - no! Tap water contains a lot more than H₂O, but we are only concerned that it MUST NOT contain chlorine or chloramine. We should also, depending on the fish breeds, worry a little about pH, the indicator of acid/alkali level. This is not desperately important as most waters are OK in this respect.
3. Other nasty chemicals. Tap water doesn't contain these naturally, but your fish will generate them. We're talking about ammonia (NH₃), nitrites (NO₂, and nitrates (NO₃). I should say that the fish create the ammonia, and other processes turn the ammonia into the other two - more on this below when we discuss the nitrogen cycle.
4. Bits and pieces. Fish will of course defecate, and may not see a spot of food, which will sink down between a couple of bits of gravel and rot away. Therefore you'll have a filter, which will pass the tank water through various layers, holding back the bits.
5. Algae. You may see a green deposit on the gravel or the stones. Nothing to worry about unless it gets to be a problem. No tank is without algae, but a handful of cute snails will usually eat it, as indeed will some fish breeds

Let's look at a couple of the above points more closely.

Point 2, tap water. As I say, the thing in tap water which the fish dislike most is chlorine. You'll smell chlorine every time you run the cold tap. So, when we first fill our aquarium, or when we exchange some old water for new, we can't use tap water straight. Apart from probably being too cold, it will contain nasty chlorine. Easy. You can buy special water treatments. In my case, when I'm about to do a water exchange I'll fill my buckets from the cold tap and add just 5ml of water conditioner per 10 litres. The bucket of treated water is left to stand for a couple of hours, both to let the conditioner neutralise the chlorine and also to let it warm up to room temp.

Point 3, nasty chemicals. When the fish, or you, or a Thompson's Gazelle urinate, it's full of ammonia. Bad, the fish don't like it, it will kill them. With the test strips you bought when you got your tank you'll check the ammonia - it should be zero. But, I hear you ask, if the fish are weeing it out constantly, how can we get it to zero? Easy. It might have taken you weeks (my small tank took 8 weeks) but you'll have cycled (see below) your tank. Very simply stated, this means you'll have established an invisible bacterial colony in the tank. These guys just love ammonia, and gobble it up. Then, when they wee, or whatever the bacterial equivalent is, their urine contains nitrites instead. But wait, nitrites are also harmful to fish, and nitrite levels should also be zero. No problem, the bacterial colony also contains another type of bacteria who just delight in snacking on nitrites. These guys excrete nitrates. Now nitrates just stay there, dissolved in the water, not exactly killing the fish, but certainly causing them to say, geez guys, this isn't very nice in here. Unfortunately we haven't got a nitrate-eating bacteria, so it just builds up in the water. So you'll test the water every few days, using test strips with little blobs that change colour to indicate the chemistry levels. Ideally, you want to see: ammonia: 0, nitrites: 0, nitrates: less than 50 (the first is parts per million, the others figures are mg/litre). If you read 50 or more of nitrates it's time for a water exchange. Re-read the previous paragraph! We'll be ditching a quarter to a third of the water and replacing it with treated room temperature tap water.

Cycling a new tank
Patience, patience, patience! You're dying to get some fish into your tank. You've put some colourful gravel in, maybe a wrecked Spanish schooner, and a little sign that say 'No Swimming!'. You've treated bucket after bucket of water, installed the filter and there's a handsome stream of bubbles going up in the corner. But no fish, no sir, not yet. You have to cycle your tank, and this might take weeks, literally. Cycling is, of course, the process of encouraging those little bacterial guys to settle in and start working.

How? You have your test strips, and, as I said, it's ammonia, nitrites and nitrates you're concerned with. Remember, ammonia is the biggie, the naughty one, the fish killer. So go out and get some and add it to the tank! (*) You want plain pure ammonia solution (it's actually a gas in its pure form), make sure it's just ammonia solution, no added soap or other cleaning aids, just ammonia. You may have to do some careful calculations, but there are calculators online which will advise you how much to add, or you can do it by trial and error, but you want to achieve 6 parts per million. Now, go to your aquarium shop and get some starter bacteria. You can buy bottles of live bacteria in a nutrient fluid - look around, you'll find it. Add the suggested amount. keep the filter running and the air bubbles if you have them, and FORGET it for at least a week to begin with. With luck, the bacteria are setting up home in the gravel and in one of the layers in your filter, porous stones which they love, and will start to eat the ammonia.

(*) Some aquarists will tell you to add fish food rather than ammonia to a new tank, on the basis that as it rots it will produce ammonia. I don't go along with that - rotting fish food may well produce ammonia, but it also produces rotten fish food, which will simply remain in the tank.

Keep an eye on the three levels. You would like to see the ammonia start to drop and the nitrites and nitrates start to rise. Add another measure of bacteria fluid weekly. Keep going until the ammonia hits zero along with the nitrites. You would expect to see a rising nitrate level by now. Once you see zero ammonia, zero nitrites and a measurable level of nitrates, add a small amount of ammonia. This should drop to zero within a day or two. You're there!

Your nitrates will be on the higher side by now if all has gone well. So now do a water exchange, replacing about a third of the water, and then add a measure of bacterial fluid. Give it a day or two, then - go and buy your starter fish! In these early stages the tank, though the chistry looks good, the tank is still settling, so you want to start with hardy fish. Ask your aquarium shop, but Zebra Danios are often quoted as being highly tolerant to a touch of ammonia and chemistry variations, and they're sweet and playful little guys.

You will now enter a cycle of measuring, checking and water exchanging. Once the tank is settled and running nicely you'll only be checking nitrites and nitrates. If nitrites are zero you can assume that the ammonia is also zero, and your task from now on will simply be to keep the nitrates down by exchanging the water. Rule of thumb: change a third of the water every week. You may also consider changing half of it occasionally, as, with the best will in the world, your filter will never provide perfect clarity.

Enjoy!

Pond Snails
Finally, I'd like to talk about pond snails for a minute. Please excuse my language, but they are bloody little shits. Once they're in your tank you have no hope of getting rid of them, like rats in the sewer, utter vermin. I have them in my big tank.

I first became infected in my first little tank, a 20 litre starter tank. A couple of albino corys and a few shrimp (all still alive and happily living in the big tank). The tank had been up and running, cycled and poulated, for a few weeks, when I decided I'd like a couple of little plants in there. Off I went to the pet supermarket and bought three small plants, two green and one red. Lovely, they looked good. Within hours, literally, I spotted a little snail in the tank. Huh? What's this? A moment's research revealed it was a pond snail. To cut a long sad story short, the tank became overrun with the buggers.

They could only have come with the plants.

In due course, deciding I like keeping fish, I bought my current big tank, 125 litres (as compared with my starter tank of 20 litres.) After cycling it and settling it I transferred my fish into it, NOTHING ELSE!! Not the plants, no gravel, nothing except the fish. Yep, you guessed, pond snails in the big tank very soon after. I can only guess that the fish were carrying snail eggs, either internally or externally, and now I have them permanently resident in the big tank. I pick out and dispose of as many as I can during water changes, but the damage is done, I'll always have them. I'm advised that, though it may be tempting to reach in and squash any you see on the glass, DON'T!! You may be simply releasing a zillion eggs. Pick them out if you can and down the sink with them. They often congregate just below the water line up in the corner where the air bubbles surface. I've invented a method of catching a load of them: I attached a very thin piece of plastic sheet to the front of a standard aquarium net. I place the plastic edge just under a horde and brush them into the net with a small brush. I can catch dozens at a time. Bastards.

When I decommissioned that little tank in preparation for throwing it away (I thought I would never be able to rid it of snails and their eggs so it had to be thrown away) I discovered scores and scores, no, hundreds and hundreds, of juvenile snails in the gravel. Presumably that's where their eggs hatch.

Just very recently, having popped into the same pet supermarket for some rabbit pellets (!) I wandered around and looked at the fish. Then I looked at their aquatic plants. What do I see, sitting on the plants and laughing at me? Yes, pond snails. This is absolutely unforgiveable in a pet shop. So innocents are going in the store, saying, Oh, those plants are pretty, let's get a couple for the aquarium. They don't know what they're letting themselves in for. For your protection, and that of your tank, I will now name names:

Pets at Home

DO NOT buy aquatic plants there! Let's possibly even go so far as to say don't buy fish there, as, who knows, they may be carrying the eggs. I'll repeat this:

do NOT buy anything aquatic at:

Pets at Home

You DO NOT want pond snails. Do NOT shop at:

Pets at Home

You have been warned.