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Pumice as filtration Medium


DiverJohn

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Different subject following on from another post....

Purchased a 2nd hand tank with a DIY external filter with about 15l of what i thought could be Effisubstrat.

Opps Good Job I rang the seller!!! I recalled he mentioned he kept cichlids, and my recollection from reading a very informative website :wink: was that cichlids like alkaline conditions and that maybe the substrate wasnt what i thot it was - it turns out to be plain old pumince.

So doing a google.com on "aquarium filtration pumice" turned up #1 piece of info was from the same website I was just about to search! (on a side not maybe that why I see so many international members :hail: )

Anybody with any experience running this stuff? How long does it take to stop leaching? Any advise welcome...

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Freshwest means this bit from Warren...

You can smash up pumice. It has a very high surface area compared to most hard surface media. It’s also free if you can find some.

It can contain silicates and heavy metals however. After smashing it up it needs to be treated. I've used it a lot with very good success. Here's how I prepare it:

Smash the pumice into bits about 10mm in size.

Soak the pumice in acid for 1 week, stirring daily.

Rinse the pumice and soak in chlorine for 1 week.

Rinse very thoroughly.

Pumice is now ready.

The acid can be anything fairly toxic. I usually use Hydrochloric Acid since I keep some in the shed. You could use acetic acid (white vinegar) but it’s a lot weaker.

The best would probably be phosphoric acid, as it will get most of the silicates and heavy metals.

You can use any Sodium Hypochlorite based Bleach as a source of chlorine. This will help break down any remaining organic material and bleach the pumice so it is very white.

The final rinsing process consists of a very thorough rinse followed by soaking the pumice for a few days, changing the water every day. When there is no smell it is ready.

Pumice works really well but sometimes it can cause a little brown algae (due to silicates) for the first couple of months. It’s normal to get some brown algae in a new tank anyway, its just a little worse for a little longer. If you are happy to put up with this in exchange for almost free media it’s an excellent option.

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We're pretty luck here to have an industrial chemical supplier. They'll supply some acids to anyone but not all acids... You'll have a pretty hard time getting hydrofluoric acid for example. I wouldn't recommend playing with this stuff anyway. It eats glass and is absorbed directly into your blood through the skin if you get a splash. It doesn't take much and you're dead. Phosphoric is quite readily available as an anti-rust agent for treating steel. If you use a steel treatment, make sure it is pure / straight phosphoric acid. Many steel treatments have other chemicals added to enhance the performance. Sulphuric acid is another good one but it’s very dangerous too.

I'd go with hydrochloric 33%. It's pretty readily available. Most pool shops should have it as a pH adjuster. Mix about 1L into 10L of water and you’ve got a strong enough solution. Keep the bucket somewhere safe while you’re soaking the pumice as it’s still strong enough to burn. You can put your hand in it but it will start to tingle within a few seconds. You’re ok if you wash it off straight away. Next best readily available acid is probably white vinegar. I don't know what concentration to use as I've never used it. I'd guess at about 2 to 1 with water...

When using any acids, use rubber gloves. If you feel a slight burning or tingling sensation go wash the area immediately. Treat it like a burn, lots of cold water. Don't buy acids that are too concentrated. Under no circumstances play with any acid if you don't know exactly what you are doing.

Eg, if you by concentrated sulphuric acid and try to add water to it, be prepared for a trip to hospital... However, if you slowly add a little sulphuric acid to lots of water you'll be ok.

Again, be very careful with acid!!

Pumice is pretty inert and doesn't seem to modify the pH at all. Because it's so porous it can store all sorts of muck. If not properly cleaned the muck will come out or dissolve into the water. This could change the pH or pollute the tank. If the muck is organic it may even cause an ammonia and/or nitrite spike...

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