Hi,

Previously I had a 4ft planted tank, after several months, it was infected by BBA and brown algae badly due to over dosing of PMDD, trying to put in SAE, Yamato shrimp, oto, CAE, molly, etc that claims to be algae eater, none of them survive even with a proper acclimation but all the fishes inside the tank(rummy nose, neon tetra, black neon, cherry barbs, etc, more than 100) are doing just fine.

Due to some reason, the tank need to be tear down, during the process a lot of fishes gone , left roughly 1x now and move them to a new setup 2ft planted tank. They all doing just fine in there, except the rummy nose get tension all the time (guess the tank too small for them).

Alright, new tank, new water (a month old), others all remain old stuff from the previous 4ft tank.

Been introduced:
4 oto in, now left 1 (after 2 weeks).
5 yamato, all gone (after 2 weeks).
4 SAE, left 2 (after several days and both of them are not active, all day long just sleeping).
2 zebra snail, still there but not moving at all (climb to the top of the water surface and stay there for days).

My tank having some common brown algae that happen to most new tank so I definitely need some fish/shrimp/snail to help out a little bit like on the plants but it seem like the nightmare still there, whenever I tried to put something new to the tank, it can't last for too long while those inside were in perfect condition. Acclimation seem to be alright but I just can't figure out what happen, I've been into fish keeping for many years, never check any NO2, NO3, PO4 or ammonia before, just some PH checking all these while but due to this incident happen too often recently, it break my confident and thinking to get some test kit to ensure my tank is stable.

1) What test kit should I get and what figure is best for fishes/shrimp/snail?

2) Will water flow too strong affect? I'm using my previous 4ft canister filter on the 2ft but water flow adjusted to half of the output.

Thanks in advance for all the help.