Caring for fish in aquarium of plastic bottle

The initial goal of placing guppies in a small aquarium was to save newborn guppy babies from being eaten by adult fish.

I’ve had positive results — all fry have survived.

I’ve also checked the possibility of using small sized aquariums as a temporary house for guppy couples with newborn babies. Fish were kept 5–15 weeks without any visible physical harm or prolonged changes in their behavior.

Here are 4 out of 5 aquariums with the adult fish on the day before I put them back into the large aquarium. I keep fry in small aquariums for now…

The 1st small aquarium was made in July 2016. The inner dimensions of this aquarium are 110/110/140 mm or about 1.6 liters.

Then I built 4 aquariums out of 2 liter plastic bottles (about 1.5 liter capacity).

Better avoid bottles with fancy shapes as it’s harder to clean or make observations due to visual effects.

All aquariums were populated in the same way: a pair of adult guppies (a male and a pregnant female); a couple of freshwater snails; 2–4 types of plants, and some rocks.

The first days of adaptation are the most difficult for guppies. Fish tend to hide or stay in one place.

The fish behavior returns to normal in a matter of days. It’s a good sign.

Heaters may damage plastic bottles :(

The thermostat in my apartment is set on 72 F (22 C) all year around. It stays between 70 F and 78 F (21–25 C). It is a comfortable temperature for a guppy. Conveniently, I don’t have to use heaters for aquariums.

Avoid direct sun :(

The small aquarium gets quickly overheated — it can kill fish.

Oxygen (O2) is provided by plants and the open water surface, just as in nature. No air pumps necessary.

Filtering is done by plants, snails, and physical removal of the residue.

Plants absorb ammonia (NH3), carbon dioxide (CO2), and nutrition dissolved in the water (competing with algae!).

Snails consume fish poop and algae.

Drain about 100–150 ml of water from the bottom of each tank weekly. Add clean dechlorinated water to restore the water level.

There are two ways to add water.

Pour water from the top. It could disturb everything in the tank.

Or use the tube for reverse draining! Drain the water from the cup into the aquarium.

First, you have to drain some water from the tank into the cup with clean water (it removes air from the tube).

Submerge the end of the tube in the clean water.

Elevate the cup above the water level of the aquarium. The water flows from the cup to the bottom of the aquarium.


A regular food diet for my fish consists of: TetraFin goldfish flakes plus, home cooked seaweed, water plants, and all the creatures that come with it.

Those are interesting creatures on their own.

Amount and number of feedings varies from 0 to 2 times daily. The amount of food should be consumed in 2–3 minutes. Reduce the amount of food if fish take more time to eat, or skip feeding if fish do not eat at all.

Here you can see the oldest babies born and grown in this aquarium.


I use water plants from the lakes of Central park of NY: duckweed (on the water’s surface),

some plant that looks like guppy grass (submerged),

and some plant that looks like java moss (bottom of the tank).

Also, I’ve been growing house plants (peace lily, aloe, and some others) in the aquariums.

The small aquarium ecosystem is very sensitive to changes. Making slight adjustments over a longer period of time works better. It allows better adaptation of fish and plants. Monitor fish activity (behavior) and plant growth for feedback on the changes.

Maintaining balance in a small aquarium is difficult and at times frustrating. Nevertheless it is possible and the end result is a beautiful world created by none other than YOU!

The intention of this video is to share gained knowledge for future improvements and your consideration.

Have fun and Happy fish :)

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