I am having trouble keeping a stable number of happy fish in my heated 35 l biube. I did have 3 minnows, 2 danios and 3 red phantom tetra - which seemed to be fine for a couple of months but as I added over time a couple of swordtails, a penguin tetra and a glow light, the danios died one after the other and then the minnows too.
Then recently I added 4 neon tetra which were bullied by the glow light, losing their tails and died one by one over a period of 2 weeks For a few weeks I had only 3 phantom tetra, 1 glow light, 1 penguin tetra and 1 sword tail. Now one of the phantom tetra has become aggressive with all the other fish, eating their tails and one of the phantom tetra has now died. I can't bear to see the other fish die one by one!
I take pains to change 10% of water as advised every couple of weeks, make the water safe, maintain the tank at 24-25 C and change filters as prescribed by biube.
However algae still seems to form rapidly and obviously the fish aren't happy!
Any advice gratefully received.