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I have a Marineland Eclipse System 12 tank and want to keep a school of corys in it. How many would you recommend I could keep safely with weekly water changes. What type of fish would you suggest for the top of the tank, its 17" high, have to be compatible with the corys. What kind of decor for the corys, driftwood?
Thanks Guys

There are PLENTY of choice for companions, it's very much up to you to choose some fish that aren't too big or too agressive.

As to how many Cory's, we'd need to know the floor-space of the tank: 21 x 11.5 inches. So that's sufficient to keep around 10-15 corys if they are by themselves, I'd say. Obviously, adding other fish will reduce this number by some amount, depending on the size of the fish.

My rule towards size of fish says that the tank should be at least 4L x 2L x 2L, which means that the tank you have would be OK for fish up to just over 5.5" (shortest side is 11 inches and a bit). Keep this in mind, and check the maximum size before you buy the fish...

Also, a very important factor is the water condition (temperature, hardness, pH) that you keep in the tank, as most fish have an ideal water condition, and you should try to keep fish that have similar needs and wants for water condition (as well as obviously being compatible with your fish).

And weekly water changes is all good, but what really counts is the nitrate level of the tank... It should be below 50 ppm for sure, and lower than 10 is ideal. That's obviously IMPOSSIBLE, if your tapwater is higher than 10ppm [like what I've got]. The best way to determine how much fish you can keep is to gradually build up the stock, and check the nitrate levels in the tank. When you start getting clsoe to 50 ppm at the end of the week (just before you do a water change), you need to stop adding fish to the tank - or increase the water change... And of course, bear in mind that the fish will grow larger than the size when you buy them...

At this point, I can't really make any particular recommendations for fish. Thre are literally THOUSANDS of differeny fish that COULD BE good companions for your Cory's, but without knowing more about what you'd like to keep, and what water conditions you have, etc, etc, it's just as likely that my suggestions would be wrong in one way or another...

Decor is very much personal taste. The Cory's don't really care what the decor is as long as the substrate is nice to their barbels, so no sharp gravel. Sand or fine gravel is often preferred because they can dig in it, which is the normal way for this fish to find food.

Driftwood is a nice, natural material, and it has added advantage of making the water slightly more acidic, which is how most cory's prefer the water. Some wood also stain the water to a slightly brown tint, which is what's called Blackwater in nature, and some corys come from blackwater in nature. Others don't. The common species, however, are all tank-bred and thus are not "used to" heavily stained water conditions, so unless you know what species you have, I'd recommend you avoid this condition. But other than that, Cory's don't actually care much...

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Mats

Thanks Mats, you're advice sounds right on. Been keeping cichlids for 20 years but not much experience with catfish except synodontis. The tank is 21"L 11.5"W 17.5H and I plan on using well washed play sand for the substrate. Was thinking about 10 corys all the same type so they will school together, they're are great sight to watch they're antics. Since the tank is high I was thinking some kind of neons maybe cardinals or black neons, something small and non aggressive for schooling fish and to add somemore color to the tank. Ph is 7.2 and the water is moderately soft so I think they will be okay. Thinking maybe panda corys or juli if I can find them. Anyway thanks for your advice and interest in a new guy. Good luck to you!!!!!!!:D

You'll probably struggle to find REAL , but "false" ones in the form of would probably not be too hard to find - my local shop have them in stock regularly, and they aren't anything like a big shop, nor do they commonly stock unusual/expensive/rare fish.

My favourite is the , and they would go well with for example cardinals or neons, as they'll all like slightly warmer water. Many cories prefer cooler water, around 22-24'C/72-76'F, whilst sterbai are happy up to around 28'C/82'F.

Cories are actually fairly ok with bigger fish too, but of course having a fairly small tank, that's not such a great idea... I have my C. sterbai together with 4+" Satanoperca leucosticta, 4-6" and four different species of Loricariidae (pleco's for those not so familiar with scientific names).

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Mats

Thanks again Matt sounds like sterbai may be a good idea with cardinals or neons I'll check them out. By the way, beautiful tank you have in your photos!

Am I missing something here.

Lets assume the tank is 2ft x 1ft (or about 50 litres) - this is about 12 gallon - I thought the rule of thumb was 1 inch fish per gallon - most corys are in the 2 - 3 inch range so you could put 6 (at 2 inch adult size) and 4 (if larger species) - so how come we are talking about 10 - 15 fish. I have 2 sterbai, 2 brochis splendens and 4 bronze in a tank with a footprint of 32 x 16 - I will not have anymore as I beleive this is fairer use of space...

So Tricky, you would recommend sticking to the one inch of fish for each gallon of water

Absolutely!

My advice is based on the information given by Ian Fuller who when I stated "a good rule of thumb is one fish per gallon" that this is not a good measure for Cory's. They will be fine in a more crowded environment. How many can fit in a particular space is perhaps a bit more difficult to say...

And it isn't a good rule in general. For one thing, a Gallon isn't the same size in the US and the UK - there's about 20% difference between them. Now does that mean that we should have 20% more fish in the UK 20g tank than the US 20g tank, or are the fish mostly concerned with how many gallons the tank is, not the actual volume of water.

I'm still sure that the best measure for how much fish you can keep are two things:
1. Nitrate levels [which I did explain in my post above] being reasonabe with the stock being kept - if the nitrate level is low, there's no reason to NOT stock the tank further.
2. Fish looking happy - this is of course the NUMBER 1 indicator. If the fish aren't happy, then something needs to be done.

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Mats