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3 Posts
Discussion Starter #1
Hey there everyone, I have been keeping fish for 2 years, and I have been keeping a community aquarium now for 1 year. After the recent addition of a male molly, I started noticing small fish swimming around and now I'm afraid my 20 gallon fish tank is becoming overstocked.

The inhabitants:

6 neon tetras(~1 inch each)
2 black/yellow tetras(~1 inch each)
5 other fish(multiple types, forgot names,put while cycling, ~1 inch each)
3 black mollys(~1.5-2 inches each)
1 silver molly(~2 inches)
1 golden algae eater(3 inches)
3 black molly fry(<.5 inches each)

9 freshwater clams(~.5-1 inches each, filter feeders)
4 ghost shrimp(~1 inch each, they clean up leftovers + fishpoop)
2 red-claw crabs(~1 inch each)
2 small amazon frogbits(new additions)

I tried to create a balanced ecosystem in my fishtank, and so I added a variety of creatures. My filter setup has 3 mediums that bacteria(and some fungi I think) have established in(1 foam thing and 2 old carbon filters). I never change them anymore in hope that bacteria takes care of all the work for me. The last medium has little bacteria, is that a good sign that ammonia is under control? Also, how much impact do clams have on water cleanness?

Love the algae eater btw. He's a little aggressive towards fish that get too near(specially mollies), but he doesn't hurt them or eat them. Definitely more interesting than the black ones that chill on the glass.

So, is it overstocked, or when will it? Thanks!

Also, are there any other organisms out there that will help clean my tank? Like sponges or something?

211 Posts
try to figure out the names of the other 5 fish please..

But I would say no you aren't overstocked but you are at the max I would put in a 20g.. Keep up with weekly 30% or so water changes and youll be fine... All my tanks are stocked like yours and I have no issues at all..

My 27g hex for example has

8x neon tetra
4x glow light tetra
1x black skirt tetra
3x gold barb
1x red tailed shark
3x electric blue ram
1x fiddler crab
4x nerite snails
2x cory cats
3x black neon tetra
2x some other tetra I forgot the name

That's like 28 fish in my tank and none of them are sick or fighting eachother and as long as I keep up on water changes they all stay fine... My 30g is like this too cept it has 4 neons and like 15 platies and stuff..

1,134 Posts
Yeah its not really well stocked. The neons are a good option. The black/yellow tetras, i dont know what they are so i cant say if they are good or not. But most if not all tetras need a school, so that isnt good. 5 fish with no names, cant say if they are good or not. The mollies need a bigger tank, and do much better in brackish water. The chinese algae will eventually kill everything. The clams, how long have you had them? What have you been feeding them? Because 9 clams in a 20 gallon tank without special feeding isnt very good for them. The ghost shrimp are all good. The red clawed crabs need brackish water and need to get to air. Amazon frogbit is a plant so doesnt count with your stocking. So IMO it isnt well stocked.

Candymancan, that stock is pretty bad IMO.

3 Posts
Discussion Starter #4 (Edited)
I've had the yellow algea eater for about a year now and it has not grown much. The clams are beneath the substrate, and they eat all the food particles in the water down there. I can tell if one dies because air bubbles start to come out of the clam every few minutes. The crabs have access to air, and the water isn't 100% fresh(water in my area is hard, and I added a good amount of aquarium salt). The unnamed fish are basically just another type of tetra, nothing to worry about I just don't remember the exact name.

My biggest concern is yea, the mollies. The silver molly had like 20 babies..omfg. As much I hate saying it, I'm glad most of those fry are slowly disappearing.

About the algea eater killing stuff, the red-claws are the ones actually trying to hunt/kill fish to eat them. Luckily, the fish are too big for them.

119 Posts
@NHelsing- Are those unnamed fish White Cloud Mountain Minnow or Endler's Livebearers? Both are a few cents each at petstores so I'd imagine they'll be the likely chosen fish. Or even Zebra Danios? Or just post pics. They need to be IDed.

Tetras do better in schools. Replace the black/yellow ones with more neons. The larger school will feel more confident. Most stores accept trade ins.

Also, swap the mollies for platies. Constant salt in the tank can't be healthy for the rest of the fish as you have freshwater and brackish fish mixed.

What's your pH? Hardness? Neons like acidic and soft water while Mollies like basic and hard water. All your invertebrates like hard water too. The majority of tetras prefer soft acidic water.

Also, the clams will get around 3" each. So many in such a small tank might spell trouble later on down the road. Especially since they are filter feeders. I'd return six of them and buy a liquid food for them.

Your crabs are going to eat your shrimp should they catch them. Prepare for their deaths. Also, it's the shrimp that have been picking off the fry.

Also get rid of the algae eater. I had one for a few years and she killed several fish (never touched the barbs or danios but everything else was fair game). They get huge and WILL outgrow that tank (they need at least a 4ft long tank). They are also horrible algae eaters when they mature and would much prefer to snack on a fish's slime coat over algae. If you want algae control for such a small tank, go for snails. I use them for my 75 and they do great. The crabs might kill snails. I haven't kept crabs in ages so you might want to look that up.

If you really want to keep the mollies (even though they do better in larger tanks), remove all the freshwater fish and get purely brackish water fish.


@candymancan- Your Red Tail Shark needs a much larger tank.

Cory cats do better in small schools of six each (or three types each if you're mixing different types).

Swap out your Skirt tetra, black neon tetras, and unidentified ones for glowlights.

The Blue Rams are fine but might try and eat your tetras.

Gold Barbs get too large for your tank. If you must have barbs, check out Cherry Barbs as they are friendly, small, and cute. They'll hang out in the bottom of the tank.

I'm guessing your tank is more towards the acidic side? If not, it can be damaging to the long term health of your tetras. If it is more soft and acidic, your invertebrates won't fair to well in terms of longterm health.
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