Since the tank size and nitrogen cycle have been covered, we will proceed to the proper setup for goldfish. The use of plants, rocks, substrate and other miscellaneous decorations will be discussed in details to make it easier for you to understand why there are some things to consider when you select your decorations.
It has been almost every goldfish enthusiast’s dream to attempt mixing plants and goldfish together in the same tank without the latter trying to turn them into a salad bowl. Though this is a little tricky to achieve, it is not impossible to mix both contrary to popular belief that goldfish will eat almost any plant that you place in their tank. Please be sure to research every plant you like before attempting them. The use of live plants has been widely encouraged in the hobby as they help improve water quality, provide food and refuge for the fish and add up to the natural beauty of the tank setup.
The first thing to consider is the temperature. Most plants that thrive in the tropics are unable to tolerate the coldwater to subtropical (range of 58-76 degrees Fahrenheit) environment required by the goldfish. They tend to turn glassy and eventually wither away if the temperature becomes unfavorable for them.
Secondly, some plants need high lighting whereas others require moderate to low light conditions. With high lighting conditions, CO2 injection may be necessary to allow the plants to compete efficiently with the algae before algal blooms are expected which are a bane in almost every planted setup as they become unsightly in vast growths. Unfortunately, as goldfish are large oxygen consumers, the CO2 injection may not be useful here especially if your filter is creating powerful turbulence that disperses the CO2 out of the water column therefore rendering the CO2 injection useless.
Thirdly, goldfish are avid grazers. They tend to graze around the bottom in search for food. While floating plants and plants that attach to any decorations will not have an issue with this, rooted plants unfortunately are met by this problem and are likely uprooted in the process as the goldfish attempts to move the substrate aside as they dig around. If you hope to successfully establish the plants, plan ahead and start laying out the plants where they should be before you get your fish. This will give the plants a head start to firmly root themselves in their place. You could also place large rocks or weights near the roots but be sure there is aeration around that area to prevent choking the plant roots which will subsequently kill the plant.
It is wisely recommended for beginners to start with plants that are relatively easy to keep and are undemanding without the use of high lights and CO2 injection. Remember to take it slow and easy as it is important that a good and slow start will make your experience a fruitful one. For a good start, try to get floating plants such as Pistia stratiotes, hornworts, water hyacinths and duckweeds. Keep your tank open-topped as most of the plants mentioned do not like condensation droplets forming on their leaves particularly the Pistia stratiotes and will eventually rot quickly. Although the duckweeds are firm favorite salads by all goldfish, by the time they have reproduce enough to sustain their number, they will work excellently in consuming nitrate level thus improving the water quality like other species of floating plants suggested although nothing will still replace the water changes as the top method for reducing nitrate and other nutrients. The hornworts are unlikely to be consumed as they prickle the mouths of the fish as it does with other fish that are urged by the temptation to eat it. Duckweeds, water hyacinths and P. stratiotes reproduce rather quickly through runners and can quickly carpet the whole surface area so be sure to trim them out when necessary. Hornworts reproduce by cutting and with their brittle leaves and stems, they can be messy and can clog some filtration systems.
Java ferns, Java moss and anubias are also tough choices and with their rather unpleasant taste, they make wise choices for a planted goldfish setup. Although Java ferns and anubias are low light plants thus making them easier to keep than most species, they are extremely slow growers. They need to be tied with nylon thread, string or fishing line into place on a decoration but not too tightly that the rhizomes become severed. Java moss, on the other hand, do not need too much attention as it will readily attach on anything and carpet it completely so be sure to trim them down if you do not like a rather bushy plant area.
For rooted plants, a good suggestion would be an array of Cryptocoryne sp., Echinodorus sp., Vallisneria sp., Sagittaria sp., Egeria densa, Egeria canadiensis, Hygrophila sp., Nymphaea sp. And Aponogeton sp. As all are rooted plants, be sure that these are planted firmly to the substrate and the white crown is not covered entirely or the plants will suffer Cryptocoryne rot which involves the plant melting although it will eventually recover but this may take some time and is best avoided. Cryptocoryne species are far more prone to Cryptocoryne rot than anything else so avoid transplanting them around too much. Finalize the layout before you try to stick them where they should be. The first four plants mentioned reproduce by runners and can quickly carpet the setup in time depending on the conditions provided. Hygrophila sp. and Egeria sp. can be reproduced by cuttings similarly with hornworts although the latter is not purely a rooted plant and is best kept afloat. A lot of goldfish favor the Egeria densa so do not be surprised if you find this plant left with a stalk instead. The leaves are too much for the goldfish to resist. The last two plants suggested Nymphaea and Aponogeton reproduce by bulbs. The Nymphaea sp. especially is an extremely beautiful plant with lushy leaf growths and even sprout flowers on the surface if allowed so be sure not to enclose your tank with a lid if you want to see the flowers sprouting and adding up to the beauty of the goldfish setup. The bulb can be left on its own although burying it halfway down will help it establish firmly its ground. To allow the young leaves to grow well, the leafy stalks that reach the surface may need to be trimmed down and this also helps prevent clogging of the surface with too many floating plants.
If you do not opt to try live plants, you could use silk plants. Make sure your choices of fake plants do not have sharp pokes, corrosive metal strips and anything else that may potentially injure or kill your fish. Some fake plants have been known to be responsible for the tattered fins. This must be avoided if you want your fish’s fins intact.
Last but not the least before we close the plant topic, it must be noted that each person has a different experience in regards to a particular plant compared to another so what may work for one may not work for the other. This must be kept in mind at all times and consider this, goldfish are extremely personable and they tend to choose their food at their own will so it is not surprising a lone comet would chomp down water lettuce and hornworts while another avoids both plants entirely. As much as possible, be sure to test each plant and plan backups in case your attempt does not work. Some plants are quite rare and expensive so it may be advisable these ones are best avoided unless you have an unlimited source and do not mind losing a single plant or two with high market value.
Next, we turn our attention towards the use of rocks and other decorations. Considering a lot of goldfish are rather prone to injuries especially sight-challenged variants such as celestials, bubble eyes and most strains with wen growths covering their eyes completely such as ranchus and lionheads, sharp-edged decorations are best avoided to avoid injuries that may become detrimental to the health of the fish. Limestones, lava rocks and polyurethane decorations with sharp edges do not work quite well in goldfish setups at all as they tend to scrape the skin of the fish badly especially when the goldfish are in chasing rituals as they attempt to mate or play around. Small round rocks and small slates (with no sharp edges) will readily work. Some goldfish enthusiasts tend to stick to marbles, golfballs and round porcelain figurines as their fancy decorations for their setup. Whether you like it or not, it does work even though it clashes with the natural outlook that you may be looking for.