Standard size 20 gallon community tank

There is no such thing as too much filtration.

IF you can get locally bred German blue rams, they are quite hardly.
It's the wild rams that tend to be less hardy/more picky.

I think what you showed it fine for a 20 gallon tank.

You intend plants, so you don't want the additional surface agitation. A HOB will be more than enough. I only use a dual sponge filter in my 20g 29g and 33g tanks.

On the proposed fish stocking, you have some issues. Pearl Gourami attain just under five inches and should have a 3-foot tank. A basic (= high) 20g is insufficient space. Gourami and cichlids are not usually good combos anyway.

The Bolivian Ram would be OK as just one, though it too needs careful water quality. It will manage at normal tropical temperatures though (the blue needs 80F plus) which makes finding tankmates easier.

Corydoras should be in groups of five or more, never less. You are OK here with five.

Shoaling fish, you want the more sedate swimmers in this small a space, and rasbora are ideal. Increase the number though to 8 or nine with these, they are better in larger groups. Or, you could consider some of the "dwarf" species of shoaling fish. Water parameters (hardness and pH) may limit these.

The fish per gallon rule is a very rough guide but not more. The number of fish a given tank will handle depends upon factors like the species (providing for their requirements, numbers needed, level they remain in the tank) and aquascape. For example, you could easily have 15 cardinal tetra in a 20g, but not 15 zebra danio which are the same basic size.

Hope this helps.

Byron.

Can I substitute two honey gouramis for the pearl without it causing issues with a ram/cockatoo? If not I may just skip the cichlids all together

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There are exceptions, but gourami and cichlids is not normally a good mix in any tank, since the two fish groups are much alike in terms of male behaviour/aggression, territories, spawning issues, etc. But here in a 20g [which is a normal or high at 24-inch length, not a long at 30-inch, correct?] either the gourami or the cichlid will be something of a stand-out centrepiece fish, and aesthetically I would say one or the other, with suitable smaller shoaling fish. If you go with the Honeys, get a trio of one male and two females; this applies to all of the "common" gourami as it should avoid a female being continually pestered by the male if there are 2 or 3 of them. Honeys are a fairly docile species, so three is fine.

I'll be going for a pH of around 6.5- our local water is 7.9 straight out of the tap but drops to 7.2 when allowed to sit for a few hours, so I won't need to spend boatloads of money on water softeners.

Also considering adding blackwater extract- does it noticeably alter the water chemistry and promote fish colour or is it just a gimmick?

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Interesting that the tap pH of 7.9 lowers to 7.2; I will suggest this may be due to the water authority adding something to raise the pH, and this dissipates out. Usually, the CO2 in tap water causes an initial lower reading, and after out-gassing the CO2 (by letting the water sit 24 hours, or shaking it briskly) the pH will be higher and more accurate. Where I live they add sodium ash (sodium carbonate) which also is temporary. Do you happen to know the GH and KH? This you can ascertain from the water authority, likely on their website; it will tell us if the pH may lower on its own below 7, which would be good as fussing with water parameters is not as easy as it sounds. My tap is 7.0 to 7.2, but in my tanks it runs between 6 and 6.4 depending upon the specific tank.

The Blackwater Extract is intended to create water conditions similar to those of blackwater streams in South America and SE Asia. I have never used this, as my tap water is fortunately near-zero in GH and KH so it is on its own at the TDS level of these habitats. The GH and TDS (total dissolved solids) is one important aspect of these products, as they soften water and acidify it. But another is the introduction of tannins that colours the water. Using chunks of wood, peat and dried leaves does the same. Wood normally wears out after an initial staining, so with weekly water changes you don't even see it after a few weeks. My suggestion here would be to set up the tank and see what happens to the water chemistry naturally. Chunks of wood can be an important part of the aquascape and will aid in this. Adding dried leaves such as oak or beech on the substrate can also affect things, and they look very natural for these types of fish.

As for fish colours, I would suspect that they will improve a bit. But this will also happen with soft water, dim light, a "natural" aquascape (to the fish) and floating plants. Over some 25 or more years of keeping soft water fish in planted tanks, I have certainly observed increased fish colouration in dimmer light. There is a reason for this that I won't go into unless you ask, as it involves the physiology of forest fish and their dislike of bright overhead lighting, and it is a physiological response [meaning, not controllable by the fish mentally] as much as a deliberate one on the part of the fish.

Byron.

kumar420 said:

Update: got a few bunches of plants- 3 small amazon swords, a corkscrew vallisneria and several stalks of some plant with reddish leaves (narrow oval pinkish red, not a red ludwigia)

I'll find out from big al's about the GH and KH and check the ottawa water site for details

As far as fish go, I was thinking of skipping the gouramis (I love them but am looking for something different) and perhaps getting some extra fish for the shoal and adding a cory or two, in addition to a single blue/ bolivian ram (the cockatoos I saw at the store looked to be all females)

So say maybe 9-10 rasboras, 1 ram or a pair, 5 cories

Can I add a clown pleco instead of the otos? I've been looking up the profile on several sites and it says they rarely exceed four inches. As for the meaty diet I will be giving them bloodworms (frozen) and maybe for the pleco a chunk of frozen shrimp once or twice a week. Would that be acceptable for a clown?

Also I was wondering if I could mix and match the cories, that way there is a school of multi-patterned catfish cleaning my tank

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I think the only caution here is the temperature which will depend upon the ram/apisto. The common or blue ram needs warmth, 80F or above. Most (but not all) corys will be stressed with this. The Bolivian is fine at 76-77F as are most corys. You can mix the corys, though it is best to try and get at least 2-3 of the same species. But they tend to be OK just as long as there are several of them, 5+ in total.

If the Clown Pleco is the true Clown, Panaqolus maccus, it reaches 3-4 inches. Another pleco is also sometimes called "Clown," and that is the Sailfin, Pterygoplichthys gibbiceps, which reaches up to 18 inches. Common names can be confusing. The true Clown must have wood for its digestion, so some chunks of bogwood; it is not much of an algae eater, and will often remain hidden depending upon the individual fish and its surroundings.

I didn't see otos mentioned previously; with this fish, let the aquarium become established (2-3 months), with some algae, as these fish are often nearly starved and they must have algae or they often die. Once settled, they easily turn to sinking vegetable foods, or fresh blanched veggies.

Without a photo it is hard to pinpoint your plant, but assuming it is a stem plant, with elongated leaves that are pinkish red, Ludwigia repens does come to mind first. Perhaps Alternanthera reineckii.