Question
Dear Sir,

I have a 70 Litres 24x12x14 tank with a under gravel filter and an air pump.

From what I understand common goldfishes such as Comet or Shubunkin will grow up to 20 - 30 inches long, but fancy goldfishes such as Black Moor or Oranda will only grow up to 5 inches long, which is its maximum size, please correct me if I am wrong.

I only plan to buy large (about 5 inches long) fancy goldfishes such as Black Moor, Oranda, etc

Now my question is according to my case, how many large (about 5 inches long) fancy goldfish should I have in that tank?

I also plan to put a goldfish plate in that tank as well, one of my friend told me that Amazon Sword are great for goldfish, however another friend told me that I shouldn't have plates in a goldfish tank. Therefore are plates suitable for my case? If so, what kind plates do you think I should buy?

Also what types of Gravels is suitable in my case?

Please help me out, Thank you very much.

Tommy

Answer
Your tank is about 18 gallons US.  Single-finned goldfish which include common, comet, and shubunkin can grow to about 12-14 inches and rarely larger.  Fancy goldfish such as fantails, moors, and orandas are usually much smaller and grow to about 8 inches as adults.  There are exceptions.  See this site for one BIG oranda:
http://hometown.aol.com/_ht_a/kmam1/Mypond/GiantGoldfish.html
The experts say that adult goldfish of any sort should have at least 10 gallons a piece.  Smaller ones can do with one per 5 gallons (and of course more for fry and youngins).  So, for 5" fish in 18 gallons, you could put in two.  If you put in three, it would probably work as well but you'd need to have a better filter than an undergravel filter.  While they do provide a lot of surface area for beneficial bacteria, they will quickly clog up with goldfish waste and foods and host bad bacteria as well.  I suggest a hang-on-tank filter such as the Marineland Penguin 170 for an 18 gallon tank.

Some plates are non-toxic while others are toxic.  Without lab testing (we actually have tested some plates here at my job), you won't know.  Some have a lot of lead which can leach into the tank.  Others have toxic paints.  Many are inert.  It really depends on each individual plate and what it's made of.  Many ceramics sold for human consumption made in the US are ok while most from places like China may be a problem.

Amazon swords aren't that great tasting as far as plants fish want to eat but most goldfish will eat them anyway.  If you want plants they love to eat, try anacharis, cabomba, hornwort, and other coldwater plants.  Plants they aren't supposed to like (but my goldfish ate them all!) include java moss, java fern, anubias, and crypts.

As for gravel, any store bought aquarium-safe gravel that is about 0.5 to 1.5 cm in diameter should be fine.  If you want to try non-store-bought gravel, it must be inert and disinfected (such as with dilute bleach for a day followed by fresh water with dechlorinator).  Quartz, shale, and other inert rocks work.  Don't use limestone, sandstone, or other rocks that release things into the water.  If you put a little acid (vinegar for example) on a sample of the gravel in question, if any fizzing occurs, don't use it.  You can also use sand or course sand (mini gravel) but not if you have an undergravel filter.

Robyn
fishpondinfo.com