Fernando wrote:
Hi,
i've been facing algae problems for some time, i first bought an
alguicide which had very little results and used the tipical magnet
brush (by the way, which way is suposed to clean algae: the soft one
or the spicky one? i've tried both!). But algae continue to grow, and
some plants have become weak and grow very slowly. I'm planning on
buying some algae eaters and some product to reduce nitrates...

The guy from the fish shop told me about two algae eaters types: one
for brown algae and another one for green-filamented ones, i'm not
sure if i should buy some of each kind or what... which ones give best
results?
and how many should i put if i have a 66 l./17 gal. with about 30
guppies?

Also, do nitrates-reducing products work well? and why could be that
plants grow higher at sides that at the center?

First off, put down the chemicals and algae eaters and step back a bit.
You need to get an overall picture of the setup of your tank to determine
why the plants are not thriving. Throwing this or that in without
considering the setup is at best just a bandaid solution. So, go back to
the basics.

What kind of lighting do you have (wattage, brand of bulbs, etc)?
What kind of plants do you have?
What is your substrate?
Do you have CO2 injection? If so, describe the setup.
Do you dose with nutrients? If so, what brand or DIY formula and how much?
Have you tested your water for phosphates?