Collecting Rain Water

When it comes to filling your shrimp tank with water (or changing water or topping up) you have four options.

1) Rainwater

2) RO water (more about this later)

3) Tap water

4) Bottled water.

Tap water and the things to watch out for.

The easy option is tap water. I started my first tank using tap water. Anything from the tap has been through a massive chemical clean up to make it fit for human consumption. Chemicals which are added vary in different countries. They can include a range of things including adding chlorine (and chloramine) and ammonia.  That’s right – the key things you don’t want (unless you want dead aquatic animals).  If you have old copper pipes – then you can add copper to the list of nasties.

So, you then need a de-chlorinator liquid to add. These liquids usually get rid of both Chlorine and Chloramine – BUT check the table as there are some which are chlorine only.

Chlorine, eventually, will dissipate if you leave tap water for long enough (24 hrs or more depending on the amount/surface area). Chloramine is a problem because it is a mix of chlorine and ammonia. This will not dissipate and will kill aquatic life.

Using these liquids can bring up bad results on ammonia test kits – unless they actually measure both free and ionised ammonia (NH3 and NH4+)

Tap water for us is monitored – we are on a water meter so it would cost us to money we didn’t need to spend.

The main problem is the pH – our water is very hard and has a high pH – so high that the shrimps were not coping very well. So for healthier animals, we switched to rainwater.

RO units – why I didn’t choose these.

The cost of purchasing the unit, and nowhere to put it were the main two factors for me.


RO water (Reverse Osmosis) is a way of passing water through a group of filters at high pressure. Dissolved organic solids are removed from the water through a membrane to remove impurities. It can involve a number of stages (from 3 to 6) which the water passes through.

How effective they are depends on the filter stages, water temperature and pressure from your mains supply. They can cost £40  to £400.

Filters include sediment, carbon and the membrane itself.

The pH is close to neutral and the TDS (total dissolved solids) measures around 0. Once impurities are removed, water must then be re-mineralized to the level that the aquatic animals need.


  • Pure water –  99% removal with higher end units. TDS around 0
  • Don’t use electricity – they run on your water pressure.


  • Plumbing it it – Installation is usually under a sink as it needs to attach to your water supply.
  • Uses tap water – so the expense of that water.
  • Can be slow – can take 12-24 hours to produce enough.
  • You need to keep the filters wet.
  • You will need a pressure pump if sending rainwater through it.
  • many require a connection to a drain for wastewater
  • Up to 50% reduction in the amount of water filtered if pressure and temperature are too low.
  • Filters need replacing every 4-6 months or as stated on the product
  • Units need maintenance – lubrication, filter replacement, replacement parts and flow valves.
  • Storage is needed for the clean water.


Rain Water – why I chose this method

The benefits:

  • Free (as a source)
  • Better for aquatic life
  • Better for the environment
  • Easy to add minerals to in the concentration that shrimp prefer.
  • No need to use chemical or chloramine removers.

Disadvantages are:

  • Not as pure as RO (TDS around 50)
  • Initial cost / time adding a way to collect it
  • Initial cost of making a filtering unit and buying a filter canister
  • Running outside every time it’s raining!
  • Storing the filtered and dirty collected rainwater
  • Time filtering it.
  • Storage

The benefits outweighed the effort and intial cost – simple as that.

How we collect and prepare the water.


First collecting it

  1. We set up a flexible pipe coming from the drain pipe
  2. Wait until it has rained hard for about 20 minutes (once the rubbish has been washed off the roof and the rain is less likely to bring with it pollutants from the air)
  3. Stick the pipe into a cheap collecting container to collect the rain.

These are 10L containers of food grade Polyethylene (so they are UN tested for Leaks and Impacts and certified safe for food storage). You get two for around £8. If it’s safe for humans it’s safe for shrimps! These are also stackable and very robust. We have about 6.




Next we filter it.

1) At a time that is convenient, we tip the water into our sediment filtration system and collect it in a clean container labelled ‘filtered water only’ containers.

I was only concerned with filtering out particles and do not run the water through carbon – although you could add another level of filtration. We store the unit in the garage and it takes a few minutes to filter 10L

The water flows, under gravity, into the filter canister (£22 from Vyair UK), through the 5 micron RO filter cartridge which is like a fabric/fibre roll with a hole down the middle (£7.99 for a pack of 3 and we use one a year) and out of the pipe into the container on the floor.

The filter is easily replaced – you just unscrew the canister and pop it it!

So it costs very little and produce a particle free water. Yes there could be bacteria and microbes in it but then that’s nature and a risk I’m prepared to take.

2) Sometimes I boil it – sometimes I don’t.

I sometimes boil the water before re-mineralising.  Daphnia and other organisms can still be present unless the water is boiled which seems to kill them. They aren’t harmful to shrimp but they ruin a good shrimp photo.

3) Finally I store the water in the dark until I need it to prevent algae growth.


I test the water in my aquarium. If the TDS meter says it is more than 230, I don’t add minerals – I dilute the tank with filtered rain water for top ups to lower the TDS back to what I want.

Salty_ShrimpFor water changes (or top ups if the TDS is 230), I re-mineralise. This is simply a case of adding mineral salts like this (left) until the TDS meter reads 230 or just under (depending on what it is in the tank at the time).

Then into the tank it goes!

The shrimp seem healthier, I get to choose what minerals go in and also the pH.



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s