how to detect some difficult circles and count them

i'm trying to count some colonies of bacterias and this is the result i got till now, i'm having problem at detecting them properly, i tried imfindcircles, but the range i pass detect a lot of false positives, can someone help me?

the code is:

clear variables;
close all;
warning off;
img = imread('colonies21.jpg');
imgcinza = rgb2gray(img);
equalized = adapthisteq(imgcinza);
limiar = graythresh(equalized);
imbin = imbinarize(equalized,limiar);
filled = imfill(~imbin,'holes');
imgjunta = (double(img)./255) .* filled;

imgjuntabin = rgb2gray(imgjunta) > 0.4;
imshow(imgjuntabin);

Answer 1

[Selva Karna]

Option 1:

* Change threshold level

Option 2:

* Use dialtion & Erotion Operration

[Lucas Moreira]

i want to detect all the black points aand count them, not eliminate