How to reset a tank

Resetting a tank

 For many people, resetting a tank can be a nightmare. A stable, mature tank is easy to manage, while fresh setups tend to go through a period of instability; for many folks this has meant algae outbreaks or melting plants, but both of these things can be minimized if not completely eliminated if the transition is managed well.

But does the tank really need a complete reset? Often, tanks that are overgrown or experiencing declining growth just need substrate maintenance or some trimming and replanting.

Click here to read about substrate maintenance. 

Click here to read about why trimming and replanting of new growth is important.

The main advantage of resetting an existing tank over starting from scratch is that you will likely have a mature filter and a tank with healthy plants that are adapted to your tap parameters and lighting system (assuming you do not change these as well). This means that the new setup will become stable much faster than a fresh new setup, with fewer algae problems to go through.

Key elements to manage

Plants

If you plan to replant existing plants after the reset, it is imperative that you store them in a way that minimizes stress. The wrong way to do this is to float a large number of plants in a small bucket. Overcrowding rooted plants in a small volume of water can lead to mass mortality when some plants start to deteriorate because everything is in the same medium. Without flow and CO2 injection, gas exchange is terrible. If you are going to keep plants in water for an extended period of time, change the water daily.

A much better way is to store the plants loosely in moist bags. The plants should be moist but not soaking wet. Then place the plants in a cool place (16 to 24*C); this slows down both plant and bacterial metabolism and slows down the deterioration of the plants. Even the most delicate species will usually last up to a week in this format. Hardy species can survive a few weeks. This gives you more time to manage the substrate, cycle, and other aspects of the tank. Storing plants in good condition plays a big role in avoiding melting and algae problems when they do occur - because healthy plants are algae resistant.

Don't do this; floating uprooted plants in a crowded bucket - if some decay, the whole bunch can melt.

Substrate

If you plan to change the substrate and refill the tank within a week, remember that you will not have time to fully cycle very ammonia-rich substrates such as ADA Aquasoil. This means that delicate plants will melt if you use very ammonia-rich substrates. If you still like a rich substrate like I do, I use a thin layer (0.5cm) of ammonia rich aquasoil at the bottom, but use leaner aquasoils (like Tropica) for the rest of the substrate.

If you are not planning to change 100% of the substrate (old aquasoils can be reused - keep the grains and discard the fine dust), mixing it with new soil is a great way to kick start the microbial community in the tank. In such a scenario, you would not want the aquasoil to dry out completely.

If you are reusing old aquasoil, it is highly recommended that you remove the accumulated organic debris. Accumulated organic waste in the substrate provides nutrients, but high levels of it will interfere with the root functions of more delicate plants. If your plants have black/brown roots that are soft, rather than white roots that are firm, this may be a sign of excessive accumulation of organic detritus in the substrate.

For folks who are resetting their tanks because of algae problems - don't dump/discard your substrate just because you're worried about algae spores in the soil. Spores are everywhere, you can't avoid algae by trying to inoculate the tank. You can only prevent algae by creating a tank environment that is unfavorable for algae growth. You can use algicides to "wipe the slate clean" in the fresh setup before adding plants/livestock.

Filter

The filter's microbial colony is invaluable to tank stability (not to mention ammonia cycling). I would suggest not cleaning it at all the same week/time you do the tank reset. This will prevent any disturbance to the microbial community, which you want to be at its optimum when you restart the tank. Also, new setups tend to produce a lot of debris; it makes sense to service the filter in the second or third week after the reset.

Using filters with a removal pre-filter allows the main chamber to be undisturbed for long periods of time.

Hardscape

If you have a hardscape that is severely affected by algae - you can bleach the rocks and then thoroughly clean them. Bleach is fairly safe as it washes off easily (unless you are using porous rock). Otherwise, if you are paranoid, you could use hydrogen peroxide instead, which breaks down harmlessly into water and oxygen over time. Normally I would just brush the wood with a hard brush - as it is absorbent, I avoid using harsh chemicals on it.

After the reset; managing the mini-cycle

Freshly submerged soils tend to release some ammonia and volatile organics, which is the main trigger for algae, and volatile soils can melt delicate plants. For example, Utricularia gramminifolia is a relatively undemanding plant, but many aquarists fail to grow it because it is sensitive to uncycled/raw soil/aquasoils.

Assuming you have stored the plants correctly as described above, you have a few days of leeway. If you have changed the substrate and are using fresh soil/aquasoil, I recommend the following: Do not plant immediately, let the tank cycle for at least a few days - run the filter, but without lights. Over the next 2 days, do large water changes (>70%) and dose bacteria cultures (if available) after the water changes. These water changes are to remove volatile organics and debris.

If you have not used overly ammonia-rich aquasoils as a base, ammonia readings should be zero by day 3 due to the use of your mature filter. If not, you can afford to wait another day or 2. You can then replant the plants you removed from the tank and start dosing, running CO2 and lights the next day. This process should minimize transition stress for the plants and mini-cycles/melting can usually be avoided. Similar to new setups, more water changes and removal of decaying old growth will help prevent algae problems as the tank matures. Using less light <60 umols of PAR on substrate in the first couple of weeks for fresh setups is also a smart tweak for folks who persistently get algae.

Click here to read about tank cycling and biology and why matured tanks face less algae issues.

Click here to read about how trimming and replanting can help solve algae issues naturally.