Stocking help

Bluebubbles · Apr 9, 2026

Setting up a 40 gallon planted and would love some help with stocking. I’m thinking of having 20 ember tetras, 10 glass catfish, 10 kuhli loach and 8 otocinclus. Is this too much?
Except for the tetras these are all new species to me so tips and tricks are very welcome.

bgarthe · Apr 9, 2026

Sounds good depending on your water parameters…..pH, GH, and KH. It’s not too much if you introduce the fish gradually/slowly over time. You might want to wait for a bit on the Otos until your tank has matured and has plenty of algae/biofilm for the Otos to eat. They really prefer to eat stuff on the plants which won’t be present yet in a newer tank. Certainly add the Otos last.
Let us know how it goes and what you decide.

jaylach · Apr 11, 2026

Totally agree that we would need to know your water chemistry before giving any specific advice.

Bluebubbles · Apr 11, 2026

Very soft water, ph around 6.6-7.9.
Tank is currently cycling. Also will be a black water tank, lots of plants, driftwood and tannins. Obviously sand sub for the loaches and thinking of doing a corner with soil to be heavily planted. Once cycled I plan on adding the school of tetras then, once stable, the loaches, then glass catfish then Otos.
Just wanted confirmation on the number of fish in the tank as I always struggle to work that out.

Naughts · Apr 11, 2026

Bluebubbles said:
Very soft water, ph around 6.6-7.9.

There are different ideas of what constitutes soft water. What is the GH, as a number and unit?
That pH range is very broad, was there a typo? What is the pH of the source water when it has been left out for 24 hours?

GaryE · Apr 13, 2026

I'm always the party killer who likes fish of the same region together, but if you can sort out the water question they should be able to live together.
There are a few species sold as glass catfish, so it's an untrustworthy name for discussion. Kryptopterus vitreolus is the most common offering, and it isn't the easiest fish to keep. I'd cross reference the temperature demands of the fish you like with its needs, and be sure you have the right water for it.

You could measure GH with a reagent kit, or if you have a cheap pen type meter, conductivity. I check the monthly reports from my city's water department. I do regular enough water changes that what I get from the tap, dechlorinated, is what my fish live in.

Death by Fish Tanks · Apr 14, 2026

That's doable. Just remember you have to feed the otto cats! The tetras may eat up all the food before the cats get their share.

jaylach · Apr 14, 2026

Death by Fish Tanks said:
That's doable. Just remember you have to feed the otto cats! The tetras may eat up all the food before the cats get their share.

If the ottos will eat pellets on the substrate one could always get some fast sinking pellets. Feed the tetras and, while they are feeding, toss in some sinking pellets for the ottos. :dunno:

anewbie · Apr 14, 2026

Bluebubbles said:
Very soft water, ph around 6.6-7.9.
Tank is currently cycling. Also will be a black water tank, lots of plants, driftwood and tannins. Obviously sand sub for the loaches and thinking of doing a corner with soil to be heavily planted. Once cycled I plan on adding the school of tetras then, once stable, the loaches, then glass catfish then Otos.
Just wanted confirmation on the number of fish in the tank as I always struggle to work that out.

You do understand that blackwater is about pure water ec 20 or 30 and not about the water being dark. If your aquarium is going to be that soft then expect ph to drop quite a bit somewhere between 4.9 and 6.2 depending on the purity of your water. If you are calling your water blackwater becauase it has a lot of tannins then it is not blackwater and you should provide gh/kh/ec/tds (not all 4 values needed). Most of the fishes mentioned will be happy in that environment but the oto need a lot of biofilm so you should wait 4 or 5 months to buy them. There are several species label 'glass catfish' so you need to identify the species you will purchase for further comment on them.

I want to stress the otto want biofilm not pellets as their primary diet and a mature aquarium is needed for them though decaying leaves help a lot.

Death by Fish Tanks · Apr 14, 2026

jaylach said:
If the ottos will eat pellets on the substrate one could always get some fast sinking pellets. Feed the tetras and, while they are feeding, toss in some sinking pellets for the ottos.

I did this back when I kept tropicals, though I used wafers. Many a Pleco or otto die because keepers don't make sure the bottom feeders eat.