Concrete in Aquarium?

[metrov]

Hi,

Does anyone know the pros and cons of using concrete in an aquarium? I have a 100 gallon, fresh water tank with a couple of large decorative objects inside made of concrete -- a Buddha head, and an Angel.

My water always tests very high alkalinity. I keep trying to lower it with PH adjusters, and it won't budge. I'm beginning to wonder if it's from the concrete objects? Also, it seems a lot of my fish die for no apparent reason, because the water otherwise tests fine.

Thanks

[Alfcea]

Concrete is basically made of calcium silicates. Since there is calcium that may be leached into the water column, you could see an increase in the hardness and the alkalinity of your water... what is the alkalinity of your tap water? And the pH?

On a related note, since concrete has a lot of silicates, same as sand and glass, you could be feeding brown diatoms...

[Northernguy]

What are some numbers from your tests?
Are the cement statues painted?
Is there any metal in the decorations,like screws or a nut and bolt?
There is a lot of different scenarios that could be the problem!
Got any pics of your tank?

Welcome to the wonderful AC!
You should go introduce yourself to everybody.

[metrov]

Hi,

Thanks for your responses. I'm at work at the moment, so I don't have any numbers. I'll have to test my tap water later on this week. [I knew that question was coming... ]

However, the concrete has no bolts or metal, just plain concrete with sand in it.

Also... what are brown diatoms? I do have some white coral pieces in the tank, and this brown algae tends to form on it. I have to take them out, and bleach them in the sun every once in awhile. Is that brown algae diatoms?

I'll get pics of the tanks, too. I would attach a .jpg to my post?

Thanks!

[Northernguy]

When you use bleach I hope you rinse it very well.Coral is extremely porous and is hard to get the bleach out!
The decorations may have toxic paint on them or some kind of sealer on them as well.
How long has your tank been set up?
Did you cycle it first?
Have you been using a dechlorinater and a stress coat of some kind?

Just curious because anything could be causing your problems!

[Alfcea]

Also... what are brown diatoms? I do have some white coral pieces in the tank, and this brown algae tends to form on it. I have to take them out, and bleach them in the sun every once in awhile. Is that brown algae diatoms?

Yes, they are. Brown "algae" is not really an algae, but diatoms...

[Northernguy]

Sorry to double post!!!

You also do not state what kind of filter you use and what kind of fish you keep and how man!!!!!!!

[james481]

I do have some white coral pieces in the tank, and this brown algae tends to form on it.

If those are real bleached coral skeletons (and not the resin reproductions) then that's probably what is causing the rising hardness and alkalinity in your water. Bleached coral will leach calcium in large amounts into your water.

[metrov]

1 -- Sorry, I didn't mean literally using liquid "bleach." I meant just leaving the coral out in the sun, and letting it "bleach" the diatoms out naturally.

2 -- I have a Seaclear system II tank: SeaClear Aquariums

3 -- The concrete has no paint on it. I'm thinking it would be best to remove the concrete objects, or coat them with resin as someone suggested.

4 -- The tank's been set up for about 9 months now. It has been cycled.

5 -- Tank holds a variety of about 20 community fish -- an angelfish, some gouramis, clown loaches; don't remember the other names.

Thanks

[metrov]

If those are real bleached coral skeletons (and not the resin reproductions) then that's probably what is causing the rising hardness and alkalinity in your water. Bleached coral will leach calcium in large amounts into your water.

I'm not sure if the coral is literally "bleached" or if it's just white coral. They are definitely not resin reproductions. They are real. Maybe they need to come out?