Help & Advice With Set Up

Hello to all. I have a Aqua Mode 300, and I am thinking of putting in a Boyu EF-05. I have a filter system that came with a Aqua Start 320. But since changing tanks, I am getting gunk build up on the ornaments far quicker than I had in the previous tank. So on a limited budget, I thought of installing a Boyu EF-05 external filtration system. This tank holds around 25ltrs of water and at the moment I have 6 fish in it, I have had the 6 cold water fish for 10 weeks now, and they seem to be in good health. Will the Boyu be ok for my needs, and what would you say how many fish would be ok in the Aqua Mode 300, I have had conflicting amounts from 2 local aquatics , ranging from 12 to 20. The tank is quite tall and I think 20 would be a bit cramp but I think 12 would seem like a right amount. I am also running a air curtain too so oxygen does not seem to be a problem, I have no live plants only plastic ones. Like I said I am a new by and any help would be taken on board. Many thanks for reading this Paul.

That's a shame!
The aqua curtain sounds interesting. Have you thought of going planted? There are some amazing photos and videos online of aquascaping, often in very small tanks, some with shrimp in rather than fish.
It can look fantastic, I think you would need a heater though for shrimp??

There are some amazing photos and videos online of aquascaping, often in very small tanks, some with shrimp in rather than fish. It can look fantastic, I think you would need a heater though for shrimp??

Beat me to the shrimp suggestion!      

I believe (although I'm probably wrong as I'm no shrimp expert) that shrimp are fairly tolerant of temperature and could be kept in 'temperate' conditions, although a heater is still recommended in such tanks just to make sure the temperature doesn't go too low.

Hello Paul  , and welcome to the forum. This fishkeeping lark is a steep learning curve, but you're in the right place for lots of good advice and flippant comments.