Filter too strong!

[MaiaB]

I recently got my first fish, 6 cardinal tetras. However one of them actually got sucked into the filter and unfortunately passed away, and they had been swimming mostly at the bottom of the tank which I thought was due to not being comfortable in the new environment yet but when I turned off the filter they were much happier, swimming everywhere. The filter I currently have is an interla filter (marina i160) and I have a 75 litre tank. I'm not sure how to make it less powerful so they won't get sucked in anymore, and if I need to buy a new one how do I know if it will be too strong or not? Any help appreciated, thank you!

 

[Essjay]

Does the manual give the turnover of the filter - it'll either be litres per hour or gallons per hour.


Healthy fish don't usually get sucked into a filter, the usual thing is that the fish is either dead or sick and too weak to swim away.

I need to check with you -
How long was the tank set up before you got the cardinals?
Did you cycle the tank before getting the cardinals? By this I mean is the tank heavily planted with live plants, or did you add ammonia to grow the filter bacteria before getting the fish.
What are the readings for ammonia and nitrite?

 

[MaiaB]

Hi, thanks for the quick reply, it says 720 litres per hour, this was the one that came with the tank so I assumed it was right, and it had been cycling for 3 weeks before I got them. It looks too strong as they all seemed to be staying in the place where it would be weakest, I didn't add ammonia and yes there are 2 large/medium plants there. Thanks

 

[FishBearer9845]

What were your results from water parameter tests? 3 weeks doesn’t sound long enough, mines been fishless cycling about 5 weeks so far and still another week to go.

 

[Essjay]

What species are the plants? Some are fast growers, others are slow growers. Fast growers take up a lot of the ammonia amde by the fish and they should be able to deal with the ammonia made by 6 cardinals. But slow growers might not.

Can I suggest you buy a liquid reagent test kit as soon as possible - they are more reliable than strips. Until you have the test kit, do 50% water changes every day. Once you have the test kits, be guided by the results and do a water change every time either ammonia or nitrite show a reading above zero.


As for the filter, that's 10 times the tank volume per hour turn over which is a lot too much. Can the flow rate be turned down? If it can't, I do suggest that you replace it, sooner rather than later as it will be growing bacteria.
I would look for a filter which does not contain carbon cartridges. Eheim make good filters (Pickup or Aquaball) as do Fluval (U series). If you want something less expensive and you have a branch of Maidenhead Aquatics nearby, their own brand Aqua-Internal 100 filter - but empty the carbon out and don't replace the sponge. All these filters have adjustable flow rates.