Moving Filter

Hi all. The angel fish saga continues. A brief precis: 2 angels and a torpedo currently living in 50L tank and have been for 18 months. 200 L is now cycling for them and appears to have completed. During this process I bought a new api kit to test the new tank and know when cycling is cmplete and I decided to test the 50L. I havebeen doing fortnightly changes, since I have had it, of around 20%. But haven't tested the water before. This was around 2 weeks ago and I discovered the nitrates were showing 250!
I have been changing around 20% every other day since then and finally the nitrates have shown signs of dropping. Now between 50 and 100.
Obviously I want to get the fish into the new tank as soon as possible as it will be a much healthier environment. People have already said not to mive them until the nitrates are lower or the shock will kill them. And somebody else said that when I do move them, to take the filter with them to help ease the transition.
My question is this: wont moving the filter with them take all the indesired nitrates with them too?

I too would like to know exactly how you've done the fishless cycle. Too many times a shop will say just add this product and it will cycle the tank when in reality it doesn't.


Nitrate usually gets high because -
There are too many fish in the tank
Water changes aren't often enough
Water changes aren't big enough
Overfeeding

In this case, the first three apply and maybe even the fourth.
Overstocking isn't just about how many inches of fish can fit in this tank. Two angels in a small volume will be stressed because they need a larger volume and the barb will also be stressed because it needs more swimming room and a group of the same fish - and I know you are aware of this and are trying to get the bigger tank ready for them.

As for points 2 and 3, with those fish in a 50 litre tank I would have been changing 50% twice a week.



Moving the filter won't move the nitrate across.
The fish will make the same amount of ammonia whatever tank they are in. You would need the bathroom the same whether you lived in a 1 bedroom flat or a mansion. In a properly cycled tank, the first bacteria turn all the ammonia into nitrite and the second bacteria turn all the nitrite into nitrate. The same fish will make the same amount of nitrate no matter what tank they are in. The difference a larger tank makes is that there is more water so the nitrate is more dilute; in a 200 litre tank the same nitrate is in 200 litres of water rather than 50 so the concentration in each litre in the 200 is a quarter of what it would be in the 50.


So as soon as you can confirm that you have cycled the bigger tank using ammonia and that 24 hours after adding a 3ppm dose of ammonia, both ammonia and nitrite are zero, you can think about moving the fish. But I would increase the water changes in the 50 litre to 35% a day. The nitrate level is now low enough for that to be safe. A couple of days of this will lower the nitrate enough to move the fish over. But only if the new tank is cycled or you'll end up doing big water changes on the 200 litre to keep ammonia and/or nitrite down.

When you bought the 50, because it already had fish the filter was already cycled.


It is possible to cycle a tank with fish rather than with ammonia. The main key to doing this is getting only a few fish to start.



To your current situation - there are almost enough bacteria in the filter in the 50 litre tank to deal with the waste from the fish already in there. The fact that you have so much nitrate shows this. The only place all that nitrate can have come from is being made by the filter bacteria. Some of the bacteria do live in the biofilm on all the other surfaces which is why I said almost enough in just the filter.
If you move the entire filter into the 200 litre at the same time as the fish, there will still be all the bacteria in the 50 litre's filter. Yes, you will lose the bacteria living in the biofilm on surfaces in the 50 litre but you may well have grown some bacteria already in the 200 litre.
But there is the extra problem of the amount of nitrate in the 50 litre. There will be lots of other things we can't measure that will be high as well. This is why we suggested doing water changes on the 50, just to get the nitrate and other things down lower. When it is just a bit higher than the nitrate in the 200 litre, it will be safe to move the fish and the filter into the larger tank. Now that you have got the nitrate quite a lot lower than it was, it is safe to do bigger water changes, and this will get the nitrate level down faster to you can move the fish sooner.

If you don't want to run two filters at the same time, the simplest way is to put the 50 litre's media into the 200 litre's filter.

Here's a useful article about cycling here http://www.thinkfish.co.uk/article/fish-or-fishless-cycling-and-aquarium-maturation, which will hopefully help you understand the process, although Sue's fantastic at explaining it and answering any questions you have.

Even if the filter in the 50-litre is completely different, that's fine - just put the media into the new filter along with additional foam/sponge or filter wool. You could cut the 'mature' media up into smaller sections with a piece of new media beside it (which you may need to cut up too, to fit the mature media around it), so that the mature media's beneficial bacteria can spread onto the new pieces of media.