Are Cement Blocks Safe to use with fish?
- Thread starter The TRUST
- Start date
I have cement blocks in all my ponds and have never had any problems at all. I use them to raise up small boulders, hold plants and hold statues.
i have a bunch of bricks in my 125, i pressure washed them b4 i put them in, waters clear and good.
Jed, I trust you mean "concrete" and not "cement." Cement is the powder that is used, along with sand, aggregate, and water, to make concrete. You don't want that stuff in your water. 
BTW, the adverse effects of concrete wash water on pH and fish health are well documented:
http://www-heb.pac.dfo-mpo.gc.ca/water_quality/fish_and_pollution/conc_char_e.htm
Obviously, the effects will be lessened once the concrete has cured, but I'd soak any concrete blocks for a long time before putting them in a pond.
BTW, the adverse effects of concrete wash water on pH and fish health are well documented:
http://www-heb.pac.dfo-mpo.gc.ca/water_quality/fish_and_pollution/conc_char_e.htm
Obviously, the effects will be lessened once the concrete has cured, but I'd soak any concrete blocks for a long time before putting them in a pond.
Here's some additional info on 'block' type materials available on the market:
Concrete block: Is a mixture of powdered portland cement, water, sand, and gravel. This produces a light gray block with a fine surface texture and a high compressive strength. A typical concrete block weighs 38-43 lb (17.2-19.5 kg). In general, the concrete mixture used for blocks has a higher percentage of sand and a lower percentage of gravel and water than the concrete mixtures used for general construction purposes. This produces a very dry, stiff mixture that holds its shape when it is removed from the block mold.
Cinder block: Is a mixture of granulated coal residue or volcanic cinders used instead of sand and gravel. This produces a dark gray block with a medium-to-coarse surface texture, good strength, good sound-deadening properties, and a higher thermal insulating value than a concrete block. A typical cinder block weighs 26-33 lb (11.8-15.0 kg).
Lightweight concrete block: Is made by replacing the sand and gravel with expanded clay, shale, or slate. Expanded clay, shale, and slate are produced by crushing the raw materials and heating them to about 2000°F (1093°C). At this temperature the material bloats, or puffs up, because of the rapid generation of gases caused by the combustion of small quantities of organic material trapped inside. A typical light-weight block weighs 22-28 lb (10.0-12.7 kg) and is used to build non-load-bearing walls and partitions. Expanded blast furnace slag, as well as natural volcanic materials such as pumice and scoria, are also used to make lightweight blocks.
In addition to the basic components, the concrete mixture used to make blocks may also contain various chemicals, called admixtures, to alter curing time, increase compressive strength, or improve workability. The mixture may have pigments added to give the blocks a uniform color throughout, or the surface of the blocks may be coated with a baked-on glaze to give a decorative effect or to provide protection against chemical attack. The glazes are usually made with a thermosetting resinous binder, silica sand, and color pigments. Admixture components/chemicals vary due to available resources and are usually not listed by any specific manufacturer.
The 'únknown' factor of the admixture chemicals is enough to prevent me from putting a $2.00 block into a tank with thousands of dollars of fish.
Concrete block: Is a mixture of powdered portland cement, water, sand, and gravel. This produces a light gray block with a fine surface texture and a high compressive strength. A typical concrete block weighs 38-43 lb (17.2-19.5 kg). In general, the concrete mixture used for blocks has a higher percentage of sand and a lower percentage of gravel and water than the concrete mixtures used for general construction purposes. This produces a very dry, stiff mixture that holds its shape when it is removed from the block mold.
Cinder block: Is a mixture of granulated coal residue or volcanic cinders used instead of sand and gravel. This produces a dark gray block with a medium-to-coarse surface texture, good strength, good sound-deadening properties, and a higher thermal insulating value than a concrete block. A typical cinder block weighs 26-33 lb (11.8-15.0 kg).
Lightweight concrete block: Is made by replacing the sand and gravel with expanded clay, shale, or slate. Expanded clay, shale, and slate are produced by crushing the raw materials and heating them to about 2000°F (1093°C). At this temperature the material bloats, or puffs up, because of the rapid generation of gases caused by the combustion of small quantities of organic material trapped inside. A typical light-weight block weighs 22-28 lb (10.0-12.7 kg) and is used to build non-load-bearing walls and partitions. Expanded blast furnace slag, as well as natural volcanic materials such as pumice and scoria, are also used to make lightweight blocks.
In addition to the basic components, the concrete mixture used to make blocks may also contain various chemicals, called admixtures, to alter curing time, increase compressive strength, or improve workability. The mixture may have pigments added to give the blocks a uniform color throughout, or the surface of the blocks may be coated with a baked-on glaze to give a decorative effect or to provide protection against chemical attack. The glazes are usually made with a thermosetting resinous binder, silica sand, and color pigments. Admixture components/chemicals vary due to available resources and are usually not listed by any specific manufacturer.
The 'únknown' factor of the admixture chemicals is enough to prevent me from putting a $2.00 block into a tank with thousands of dollars of fish.
I would soak them in a bucket and see how much the ph goes up before i would dump them in my tank and see what leeches out of it.
I made rocks from portland cement for my SW tank and had to cure them in water for 2-3 months before i could use them
I made rocks from portland cement for my SW tank and had to cure them in water for 2-3 months before i could use them
I soak them for 3 weeks before using them and never had a problem... what about terra cotta flue pipe or terra cotta bricks??? cheap and work the same.... flue pipe also gives fish a place to hide....