Wondering About My Old Tank

Hi Carl, welcome to the forum 

The first thing to do is find out how hard your water is. You should be able to find that information somewhere on your water provider's website. You need a number and the unit rather than some vague words. The unit is important as there are about half a dozen different hardness units.

The reason I say this is because you have hard water fish (guppies) and soft water fish (the rest) on your list. One or other will not be happy depending on your water hardness.

If you get cories of any species (or any other bottom dwelling fish), you'll need sand on the bottom of the tank rather than gravel. Play sand is very suitable, and cheaper than those sands sold for aquariums. Being designed for children who are quite likely to eat it, play sand is very safe. It just needs a lot of washing.



I have read your other post but I'll keep everything here.

The other good filter is the Eheim Aquaball, or even an Eheim Biopower. These are very similar filters just differing in their media.
If you plan on using the old heater, check it can keep the water temperature at what you want it. Old heaters have been known to fail.

Ammonia in tap water - water companies mostly use either chlorine or chloramine to disinfect mains water. Chlorine is an ammonia and a chlorine joined together. All dechlorinators split chlorine up then remove the chlorine, leaving the ammonia half in the water. But the amount of ammonia is nowhere near high enough for a fishless cycle. You would be better getting a bottle of ammonia and following the method on here https://forums.thinkfish.co.uk/fishtank-filtration-and-cycling/fishless-cycling-how-to-do-it/

The other alternative is to plant the tank. Plants use ammonia as their preferred source of nitrogen. In a tank with a lot of well growing plants, you don't need to cycle it first. Just wait until you know the plants are growing well, they add fish a few at a time. You do need to monitor ammonia and nitrite but if there are enough plants you shouldn't see aeither of them.


Once the tank has fish in it, when you do your weekly water change you will add new water that has ammonia in it. In this case choose a dechlorinator which 'detoxifies' ammonia. This detoxification lasts around 24 hours by which time the bacteria or plants will have removed it all. This detoxified ammonia still shows up in our test kits though.

Hardness 7.5 is actually on the soft side for fish. Moderately hard starts at 10.


Guppies' hardness range is 149 to 536 ppm, or 8.5 dH to 30 dH. We should aim to keep fish somewhere round the middle of their preferred range (We are updating the profiles as they were written a couple of decades ago but we haven't done guppies yet  )
Fish in shops are only there for a short period - or at least that's what the shop hopes - so they don't have time to be affected by the shop's water. And if they get sick after they leave the shop, they don't care because they have your money.

Is there any fish that prefers softer water than guppies that you would be prepared to substitute for them? The other fish are all fine at your hardness. There are a lot more fish available than are in the profiles on here - take a trip round all your shops and see what they stock. But don't be persuaded to buy anything, ever, without researching first. So many shops will make up any rubbish to get a sale.

There is a way to keep guppies, platies and even mollies (though they are big fish which need a large tank) and that is to add minerals to the water to make it harder. But if you do this, you can't keep any soft water fish with them.
The downside is that you have to 'harden' the new water at every water change, and make sure the amount of minerals you add get the hardness to exactly the same each time.You have to keep a supply of the minerals in the cupboard in case emergency water changes are needed.

You have time to decide what you want to do, and we can help if you decide you do want to 'harden' the water.

Hi All,

Firstly thank you all for your comments!

I have phoned my water company now as their website was very confusing as i live between 2 areas listed on their chart. Apparently i should be looking at a completely different area?!

So i now have a hardness reading of 148 mg/l or 11.1 Degrees german. Frankly i don't trust this that much anymore so will be doing tests on my own to check the hardness before any purchases. Will dechlorinator effect the hardness at all? Should I test from tap or in tank?

Thanks again all! 

Carl