A QT tank must be large enough for the fish that are to be quarantined. Since it will be running copper, it does not need live rock and will be a sterile system. It does need mechanical filterization from a hang on back filter or canister and will need weekly water changes to keep the nitrates in check.

With water changes will come the need to add more copper to maintain a proper therapeutic dose. I prefer to use complexed copper because it is less stressful on fish. Provided fish do not show signs of disease, I believe it is sufficient to quarantine new fish for two weeks, but there are many people who believe in a 5 week quarantine.

I like to use Aragonite Sand. It is available in many grain sizes and has natural buffering qualities that are good for saltwater and Cichlid tanks. I believe it is fine to buy used sand or crushed coral when available for swim tanks only.

Consider the inhabitance that you will be putting in the tank before selecting the size grain of the substrate. Many sand sifting fish like gobies and sand divers like some wrasses need to have fine sand to be happy as do stingrays and sharks.

If a tank has been treated with copper, much of that copper can be contained in the sand and this should not be used in a reef tank. Only use bagged sand for reef tanks to be sure it is not loaded with copper. If you buy unwashed sand from an existing tank, take about ½ gallon of it and leave it as is and rinse the rest well.

There is too much anaerobic bacteria and other things that have been disturbed by moving the sand and if you start with this you are likely to crash your tank. The same goes for if you move your tank and disturb the substrate.

UVs just need to have water pumping through them. You can hook them up so your return from any pump or filter sends water through them and then back to the tank. For non-drilled aquariums or ones without a canister there are hang on models available.

If the return pumps over 300GPH the UV will do fine for water clarification, but will not have a good kill rate for protozoan which helps with disease control. You also don’t need as large a UV if you are just using one for water clarification. On tanks with a sump you can just use a small submersible pump in the sump to pump water through the UV and Back to the sump.

In this case the UV can sit on top of the sump or be mounted behind it on the back or side of the stand. Bulbs should be replaced every 9-12 months even if they are still burning.

It will depend on how much water has gone through the unit and the quality of the water going through the unit. Cartridges last longer if water goes through a softener first. Some RODI units have a pressure gage on the inlet to give some indication of when the cartridges are needing to be changed based on the pressure it takes to push water through them.

The best way to know is to get a TDS meter and test the water coming out of the unit. Some of these are hand held and others go inline and both types are fairly inexpensive. When the TDS gets over 10 PPM then it is time to change cartridges. Change the carbon and sediment filters at the same time.

Change the DI every other time you change the sediment and carbon and change the RO membrane every other time you change the DI.

First you will want to replace the RO membrane and the carbon and sediment filters if the RO has been in use for some time. Next you will want to ad what is called a “piggyback” DI to your RO.

The DI housing and cartridge have an inlet and outlet and you just connect the outlet from your RO into the inlet so that water passes through the DI after leaving the RO.

When you put an overflow on a tank with a sump, the tank no longer loses any water because the water is kept at the overflow level by the return pump. The sump however loses water as the tank and sump evaporate. For salt water tanks, one chamber of the sump is reserved for the protein skimmer and maintains constant water level.

This leaves 2/3 of the sump, the refugium section and return pump section, for an evaporation reservoir. If the sump is small and does not have an auto top off float connected to a water source, then the sump will need to be topped off often, possibly too often.

A larger sump also allows for a larger refugium section to act as a bio filter with a deep sand bed and macro algae.

There are a few things to consider. If the old crushed substrate is more than three years old it would be best to replace it with new aragonite substrate. You can get this in different grain sizes.

The new substrate will have better PH buffering abilities for several years. In selecting grain size you need to consider what type of fish or inverts you will have. Many people with reef tanks prefer finer grains because many of the smaller fish and some inverts are sand sifters or burrowers and do better with fine substrate.

I like to go with special grade reef sand, rather than sugar sand because the very find sand tends not to settle as well when agitated by water movement or livestock. Some people like to use black sand, but in most cases it will make the tank look dark even with powerful lighting.

If you will be starting a reef tank, you will also need to consider if the old substrate was in a tank treated with copper. If it was in a reef tank, then it was not treated with copper, but if it was in a fish only tank then you cannot know for sure.