I'm setting up new home for my goldfish and I bought one beautiful brown volcanic stone. But now I'm not sure is it good for them, will they scratch? And how can I wash this stone? I put it in the water, but dirt comes out all the time.

sounds like it'll cloud the water really badly so it probably won't be so good for the fishies, I wouldn't put it in.

Have you tried splashing some vinegar on it to see if it bubbles? That's a good initial test.

No, but I'll try today! I bought this stone in a Pet store, where they told me it's OK for goldfish tank. But, I'm not sure because of sratching and dirt.

If the vinegar test bubbles then take it back and tell them what idiots they are

If it fizzes or bubbles, or clouds water, then it's no good for the wee fishies!

Good luck with the test,
Cheers

Volcanic stone is inert - in the way you are worrying about. And it is a common thing to use in fish tanks. BUT - and it is a big BUT - goldies (or any fish with delicate flowing tails or protruding eyes, etc.) are rather delicate. A sharp surfaced stone can easily catch and tear delicate finnage, scratch eyes, or pop scales. If the fish decide to "get frisky", the males can drive a female and body check her into the glass and everything in the tank. A female, being slammed into a sharp stone would definately not come out in good shape.

Volcanic stone, because it has sooooo many pores is GREAT for biological platforms - the surface area is amazing. But because of those pores, small pieces of stone and sand and stuff can hide - and be nearly impossible to get out of the stone. I am sure with much rinsing and shaking and such, the majority can be removed, however.

If you can return this stone, I would recommend it. It is really not a safe ornament for use in a fancy goldfish tank. IF you cannot return it, it can be very valuable for biological media. Take a hammer and smash it into smaller chunks. Those chunks, used in your filter, will be a marvelous platform for beneficial bacteria.

Thanks! I really have breeding behaviour in my tank lately, so maybe it's better to give up. What kind of stone can I put in the tank? I bought brown gravel, because I wanted some kind of natural look, with few live plants. My new setup is in progress, and at this moment tank looks too dark and depressive. And I heard that wood is also not good for goldfish . Can I buy few smaller stones and stick them together with aquarium glue?

That would certainly work. I have larger rocks and such that I found at a landscaping company. I am particularly fond of the pink quartz. I have tumbled it so it is smooth sided. Many people use "river stone" in their tanks. These can be found at local hardware stores - they are rounded inert stones.

There are also nice, larger "gravel" stones that have heen tumbled/polished that are sold - I think they are very attractive. If you have a darker stone, what about putting on a light blue background on the tank? That will brighten it up substantially.

I like building plastic plants with decorative stones glued around them. These sit on my bare-bottomed tanks - and look very nice.

Use your imagination - it sounds like you have a good one. One of the great things about a fish tank - it does not have to stay the same - you can change it as you wish!

You're right, maybe it will be easier to rearrange tank later! In our local pet stores there isn't some good choice of decorations, just few things for gf aquarium, but I found today one beautiful big red jasper stone (not polished). Can I put it in the tank? It seems safe, with few sharp edges, mostly smooth. Should I cook that stone first or just wash it?

It depends on where you found it. If in doubt, boil it for 10 minutes at a rolling boil - in salt water if you wish - and you can be comfortable that it is "clean".