Hi all,
So we have had a small 60L tank for 5 years (superfish start 70 setup with a bubbling decoration and fake plants ... I know i know but at the start my wife was hesitant as we have friends with planted tanks that got overgrown). We have had a school of cardinals which has now shrunk to 3 and I was about to buy more (and will this weekend) but have ended up with 2 new plecos. 

A friend recently had an accident with their tank causing it to leak and so I agreed to take in their two young bristlenose pleco. They are only 1-2 inch long and have chosen separate decorations to shelter in. Problem is our friend has decided they won't get a new tank.

I am very aware they will get much bigger and thankfully at the end of this month my annual bonus gets paid and I am upgrading tank. I have a nice corner spot 0.9m x 0.9m where I am going to put a ~150L cube tank, planted, nice external filter. The works and doing it properly. Budgeting over £1k.

I am feeding a mix of frozen food every couple of days plus some sinking catfish food etc. Doing a 10L water change once a week but I already can see a big uptick in waste. 

My questions:
1 - is that a big enough tank?
2 - do I need to adjust what I am doing in this immediate short term while I get the big tank set (twice a week water change/different food?)
3 - what would be good tank mates? Are the cardinals a good option or should I leave them in this tank (adding more to build the school size again) and just get new mates for the new tank?

Thanks all

Signed

A very stressed accidental pleco dad

(Pic added of upside down goofy boy)

Adopted plecos ... advice needed