Well then.....
*stretches fingers*
Shall we begin?
The fish species you are interested in are a more sensitive, SA type. Almost all of those Cichlid species will have significant problems dealing with your tap water.
1) Relatively hard water and Higher PH, will limit some species immediately.
2) The 30+ mg/L Nitrate level in the tap water clears out the rest of the list. None of those SA Cichlids will be able to tolerate your Nitrate levels that high in the aquarium.
So, you will need to provide an alternate source of freshwater for this aquarium than what is available from the tap. It's getting more expensive. But..... you may be considering entry into an aquarium 'club' that many - MANY - have joined before you. And that many are indeed in now. There are two basic types of those unusual aquarium folks. They are, Dedicated Saltwater & Dedicated Black Water. And interestingly enough, you can't find much further differences in water chemistry between the two. They both share a basic principle however. That is, the water required for the aquarium originates from Reverse Osmosis filtration.
On to it then....
TrickyD said:
I have many questions about it, what type, what capacity, do they have to stay wet when not being used ?
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Beyond 'Reverse Osmosis' I'm not sure about type. The capacity you should install is based on the anticipated, weekly water consumption. In this case, your more sensitive Cichlids will require weekly water changes to properly dilute Nitrates buildup out of the water (even when starting with zero amounts). 50% is a good weekly amount - your 450 Liter aqurium will require a minimum production capacity of 225 Liters of filtered water per week. I would consider 300 Liters+ production capacity to be more reasonable. It is good to have some extra capacity. And yes, the RO systems I've worked with have all 'stayed wet', even when not in use.
TrickyD said:
Then there is the option to buy RO water, if bought, how long can it be stored and how? Is RO water for window cleaning systems the same as that for aquariums?
Yes, RO water can be purchased. You however, are not perhaps a 'usual' customer! In this case lugging 20 Liter containers of water back and forth will certainly NOT enhance your quality of life or make you appreciate the hobby - at all! If you find a place that makes and sells RO water locally? You will need to make arrangements for them to provide a re-filling service for a water reservoir in your home. That is, running a hose probably from a truck or something that can pump the water into your water reservoir. It could be done I suppose (I've just never heard of anyone who's ever done that before...). Oh, and RO water can be stored for a very long while. It's just not a good medium for algae or bacteria to grow in, so it takes a good while for things to get started. And yes, the RO water used to clean windows is probably the same stuff you could use for an aquarium. The RO water dries without producing scale or streaks - just little H's & O's in there!
TrickyD said:
Taking into account the initial purchase price and upkeep of a RO unit, it may be more cost effective to buy the water only. Then there's rain water, how would it be treated for aquarium use, taking into account the amount of pollution here (close to London UK).
The install cost, upkeep (replacement membranes) and other things will have to be weighed against the availability and cost of purchasing RO water. And if you install, you will then have a municipal-looking filtration unit, complete with 300 - 350 Liter reservoir in your house to deal with. Not saying you can't find a somewhat aesthetically pleasing manner to place that stuff.... but still. And no, I wouldn't mess with rainwater. Plus pollutants, there are just many variables to control to inspire much confidence in that method as reliable and sustainable to use for your aquarium over the long term.
Bottom Line: You are going to have to do a basic, cost-to-benefit analysis of this problem. And in the end, it all really comes down to well,
HOW MUCH DO YOU WANT IT??? :wink: